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BIOLOGICAL  LECTURES 


DELIVERED  AT 


THE  JVIARINE    BIOLOGICAL    LABORATORY 
OF    WOOD'S    HOLL 


In  the  Summer  Session  of  189? 


Boston,  U.S.A.,  and  London 
GINN   &   COMPANY,  PUBLISHERS 

1896 


Copyright,  1896 
By  GINN  &  COMPANY 

ALL  RIGHTS  RESERVED 


CONTENTS. 


LECTURE  PAGB 

I.    Infection  and  Intoxication.     Simon  Flexner  .     .  i 

II.    Ivinmnity.     George  M.  Sternberg      ....  ii 

III.  A   Student's  Reminiscences  of  Huxley.      Henry 

Fairfield  Osborn 29 

IV.  Palcsontology  as  a  Morphological  Discipline.     W. 

B.  Scott 43 

V.    Explanations,  or  How  Phenomena  are  Interpreted. 

A.  E.  DoLBEAR 63 

VI.    Known  Relations  between  Mind  and  Matter.     A. 

E.  DoLBEAR 83 

VII.    On  the  Physical  Basis  of  A  nimal  Phosphorescence. 

S.  Watase loi 

VIII.    The   Primary    Segmentatio7i    of  the    Vertebrate 

Head.     William  A.   Locy 119 

IX.    The  Segmentation  of  the  Head.    J.  S.  Kingsley.        137 

X.    Bibliography  :  A  Study  of  Resources.     Charles 

Sedgwick  Minot 149 

XI.    The  Transformation!  of  Sporophyllary  to  Vegeta- 
tive Organs.     George  F.  Atkinson  ...        169 


95273 


Biol.  Lect.,  to  face  page  i. 


Fig. 


J  '•  vl 


^:i}>-' 


Experimental  Abscess  in  the  Kidney  of  the  Rabbit. 
Staphylococcus  pyogenes  aureus  infection. 


Fig.  II. 


.,^mi^i 


yCV 


"  1     ,.  ""',''.  . 


mi^' 


Pk. 


V.3  '^ 


Experimental  focal  cell  necrosis  in  the  liver  of  the  Guinea  pig.     Ricin  intoxication. 


FIRST    LECTURE. 


INFECTION    AND    INTOXICATION. 

SIMON    FLEXNER,    M.D. 

(Associate  Professor  of  Pathology,  Johns  Hopkins  University.) 

The  science  of  biology  in  its  widest  sense  comprises  the 
study  of  life  in  all  its  forms  and  activities,  both  normal  and 
abnormal.  For  this  reason  I  shall  not  apologize  for  bringing 
before  you  a  subject  closely  related  to  pathology,  a  branch 
which  is  concerned  only  with  the  abnormal  forms  and  activities 
of  life. 

The  underlying  principles,  which  are  to-day  the  subjects  of 
thought  and  research  in  the  branches  usually  classed  as  the 
biological  sciences,  are  not  essentially  different  from  those 
which  are  also  found  in  the  field  of  work  which  more  pecu- 
liarly belongs  to  pathology.  Nor  is  pathology  any  longer  a 
study,  the  subject  matter  of  which  is  limited  to  man  and  the 
higher  animals.  Its  application  to  the  lower  animals,  and 
even  to  plants,  has  been  so  successful  that  we  are  now 
justified  in  looking  to  the  comparative  study  of  disease  pro- 
cesses for  the  solution  of  some  of  the  many  still  obscure  prob- 
lems in  human  pathology. 

Manifestly  it  would  be  neither  possible  nor  profitable  to 
attempt  to  compass  in  so  brief  a  time  the  entire  field  of  path- 
ological research.  It  becomes  necessary,  therefore,  to  restrict 
our  attention  to  a  single  one  of  its  problems  ;  and  as  there  is  at 
the  present  time  none  which  is  attracting  more  attention  than 
that  relating  to  the  causation  and  effects  of  infectious  diseases, 
I  have  chosen  for  this  hour  the  discussion  of  one  aspect  of  this 
subject.  My  remarks  will  be  prefaced  with  a  few  general 
statements  concerning  the  parasitic  agents  of  disease.     Some 


2  BIOLOGICAL   LECTURES. 

of  these  belong  to  the  vegetable,  others  to  the  animal  king- 
dom. They  are  found  in  the  former,  among  the  fungi  and 
bacteria,  and  in  the  latter,  among  the  protozoa,  vermes,  and 
arthropods.  While,  however,  the  term  pathogenic  micro-organ- 
isms is  arbitrarily  applied  to  all  the  vegetable  parasites,  among 
the  animal  parasites  only  the  protozoa  should  properly  come 
under  this  category. 

Infectious  diseases,  then,  are  such  as  are  caused  by  pathogenic 
micro-organisms,  i.e.  by  fungi,  bacteria,  and  protozoa.  In 
speaking  of  the  bacterial  origin  of  diseases  many  writers  apply 
the  term  bacteria  to  micro-organisms  of  animal  as  well  as  of 
vegetable  origin ;  but  it  must  be  remembered  that  protozoa  are 
not  bacteria,  although  the  term  pathogenic  micro-organisms 
can  be  properly  applied  to  both.  I  wish,  therefore,  to  empha- 
size the  fact,  that  besides  the  diseases  of  bacterial  origin,  there 
are  also  others  which  are  caused  by  organisms  belonging  to 
the  animal  kingdom.  Typical  examples  of  this  class  are  found 
in  the  different  forms  of  malarial  fever  which  are  caused  by 
the  invasion  of  the  blood  and  organs  by  organisms  belonging 
to  the  group  of  protozoa. 

It  must,  however,  be  admitted  that  the  diseases  caused  by 
vegetable  parasites  are  best  understood.  This  fact  is  easily 
explained  by  our  present  successful  methods  employed  for  the 
propagation  of  these  parasites  outside  the  body,  whereas  as  yet 
the  pathogenic  protozoa  have  not  been  obtained  in  the  form  of 
pure  cultures  outside  the  bodies  of  infected  animals.  The 
growth  and  multiplication  of  the  pathogenic  micro-organisms 
are  associated  in  many  instances  with  the  production  of  cer- 
tain substances  of  a  toxic  nature,  these  poisons,  or  toxins  as 
they  are  called,  playing  a  great  role  in  the  causation  of  disease. 
Certain  non-pathogenic  or  saprophytic  micro-organisms  in  the 
course  of  their  growth  are  also  capable  of  producing  poisonous 
products.  There  is,  however,  this  marked  difference  between 
these  two  classes  of  agents,  namely,  that  whereas  the  former 
are  capable  of  living  and  of  manufacturing  the  toxins  within 
the  living  body,  the  latter  can  subsist  only  in  the  presence 
of  dead  material.  Examples  of  poisoning  by  the  products 
developed  by  saprophytic  bacteria  are  found  in  the  accounts, 


INFECTION  AND   INTOXICATION.  3 

which  we  so  often  read,  of  epidemics  occurring  suddenly  to 
large  numbers  of  persons  from  the  ingestion  of  partly  decom- 
posed meat,  fish,  sausage,  milk,  etc.  Infection  is  therefore  to  be 
distinguished  from  intoxication,  inasmuch  as  the  first  presup- 
poses the  existence  of  a  living  agent  which  enters  the  body 
and  survives  there,  while  the  second  is  to  be  attributed  to  the 
effects  of  any  toxic  agent  which  may  be  present  in  the  body  in 
sufficient  amount  to  produce  more  or  less  marked  symptoms  of 
disease.  The  relation  of  intoxication  to  infection  cannot  be 
better  expressed  than  in  the  following  paragraph.  "  It  is  im- 
possible to  draw  any  sharp  dividing  line  between  intoxication 
and  infection ;  but  it  is  believed  to  conduce  to  precision  and 
clearness  to  regard  as  agents  of  infection  only  such  as  are 
capable  of  reproduction,  that  is,  such  as  are  living  organisms 
and  not  include  among  these  agents  chemical  poisons  whether 
produced  by  bacteria  or  other  vegetable  cells  or  by  animal 
cells"  (Welch). 

There  is  perhaps  a  tendency  at  the  present  time  to  minimize 
the  importance  of  the  living  agents  themselves  in  the  produc- 
tion of  the  phenomena  of  infectious  disease,  and  to  ascribe 
these  entirely  to  the  action  of  the  toxic  agents  manufactured 
by  the  micro-organisms.  But  in  view  of  the  fact  that  in  several 
typical  infectious  diseases,  among  which  may  be  mentioned  an- 
thrax, asiatic  cholera,  and  typhoid  fever,  it  has  been  found  quite 
impossible  to  separate  in  an  active  form  the  toxic  products 
from  the  bacteria  which  produce  them,  the  latter  cannot  be 
regarded  as  less  essential  to  the  production  of  the  disease  than 
the  former.  Indeed  there  are  few  diseases  at  present  known 
in  which  all  the  symptoms  can  be  ascribed  to  the  toxic  products 
of  the  micro-organisms  alone.  To  quote  another  paragraph  from 
Dr.  Welch's  writings  :  "  In  the  case  of  most  infectious  dis- 
eases we  can  no  more  separate  the  actual  presence,  multiplica- 
tion, and  specific  vital  activities  of  the  bacteria  within  the  body 
from  the  disease  than  we  can  substitute  any  chemical  substance 
for  the  actual  presence  and  growth  of  the  yeast  fungi  in  the 
production  of  alcohol  from  sugar." 

Yet  the  role  played  by  the  chemical  substances  developed 
from  certain  bacteria  in  the  production  of  the  phenomena  of 


4  BIOLOGICAL   LECTURES. 

disease  is  not  inconsiderable,  and  we  may  safely  say  that  only 
with  such  bacteria  as  produce  toxins  of  great  potency,  which 
are  easily  yielded  by  the  cells  to  the  surrounding  medium, 
would  it  be  possible  in  a  given  disease  for  the  toxic  chemical 
substances  by  themselves  to  give  rise  to  the  same  phenomena 
as  those  which  are  due  to  the  action  of  the  living  bacteria. 

The  study  of  the  nature  and  action  of  these  toxins,  or,  as 
they  are  now  generally  called  toxalbumins,  has  added  not  a 
few  interesting  facts  to  our  knowledge  of  poisons  in  general ; 
but,  at  the  same  time,  it  must  be  understood  that  the  forms 
with  which  we  are  dealing  have  not  at  this  time  been  isolated 
in  a  state  of  absolute  purity,  although  they  have  been  obtained 
in  a  condition  of  great  potency.  Their  exact  nature  is  not  as 
yet  well  understood.  They  are  believed  by  most  bacteriolo- 
gists and  chemists  to  be  of  an  albuminous  nature,  many 
authorities  claiming  them  as  enzymes.  They  are  amorphous 
bodies  and  differ  essentially  from  the  crystallizable  ptomaines, 
with  which  substances  they  are  sometimes  confused.  Perhaps 
the  one  best  studied,  certainly  the  one  possessing  the  greatest 
potency,  is  the  toxalbumin  produced  by  the  tetanus  bacillus. 
In  the  still  impure  state  in  which  it  has  been  obtained,  its 
activity  has  been  found  to  be  simply  appalling.  A  single  dose 
of  0.000.000.05  grm.  suffices  to  produce  death  after  tetanic 
convulsions  in  a  mouse  weighing  1 5  grams,  and  it  is  estimated 
that  the  fatal  dose  for  an  adult  human  being  does  not  exceed 
0.23  mg.  You  will  appreciate  this  fact  better  if  you  remember 
that  the  fatal  dose  of  atropine  is  130  mg.,  and  of  strychnia 
from  30  to  100  mg.  It  should  further  be  mentioned  that  this 
toxalbumin,  unlike  many  of  the  others,  is  capable  of  giving  rise 
to  the  same  symptoms  as  the  bacillus  which  produces  it. 

Another  extremely  virulent,  although  less  active,  toxalbumin 
is  that  obtained  from  the  cultures  of  the  diphtheria  bacillus. 
Of  this  0.4  mg.  suffices  to  kill  eight  guinea  pigs,  each  weighing 
400  grams. 

In  contradistinction  to  the  tetanus  toxin,  that  produced  by 
the  diphtheria  bacillus  jdoes  not  reproduce  the  entire  series  of 
phenomena  of  the  disease  to  which  it  belongs,  since  the  in- 
jection of  it  does  not  produce  at  the  point  of  inoculation  an 


INFECTION  AND   INTOXICATION.  5 

actual  false  membrane.  An  extraordinary  feature  exhibited 
by  the  diphtheria  toxin  is  seen  in  the  extreme  slowness  with 
which  it  is  sometimes  known  to  act.  Whereas  the  poisonous 
chemical  agents  with  which  we  were  previously  acquainted 
exert  their  effect  quickly,  and  usually  after  a  short  interval, 
the  diphtheria  toxin  requires  at  times  weeks  and  even  months 
for  the  production  of  fatal  results  in  the  animal  inoculated. 
For  a  time  it  stood  alone  in  this  regard,  but  I  have  found 
similar  delay  in  the  action  of  another  toxalbumin,  —  ricin,  a 
substance  yielded  by  the  seeds  of  the  ricinus  communis  (castor 
plant). 

Recent  studies  have  shown  that  the  toxalbumins  are  widely 
distributed  in  nature.  Thus  far  they  have  been  found  among 
the  lower  and  higher  vegetable  forms,  and  even  in  the  blood  of 
various  animals,  such  as  the  eel,  snake,  and  dog. 

When  we  proceed  to  study  the  effects  of  these  pathogenic 
agents  upon  the  animal  body,  we  find  that  the  phenomena 
which  are  caused  by  the  toxins  can  often  be  distinguished 
from  those  due  to  the  actual  presence  of  the  bacteria  themselves. 

Two  main  forms  of  lesions  of  cells  can  be  distinguished  in 
infectious  diseases.  In  the  one,  most  or  all  of  the  cells  are 
affected  ;  the  lesion  is  diffuse,  and  shows  itself  by  an  increase 
in  the  size  and  granulations  of  the  cells,  associated  often  with 
the  appearance  of  globules  of  fat  in  those  otherwise  free  from 
this  substance,  or  with  an  increase  of  it  in  those  already  con- 
taining it.  In  this  way  is  brought  about  the  so-called  paren- 
chymatous degeneration  of  cells,  which  in  extreme  cases  may 
lead  to  actual  cell  death  (necrosis).  This  is  the  typical  lesion 
ascribed  to  the  action  of  chemical  substances.  It  is  found  in 
all  infectious  diseases  and  in  many  forms  of  intoxication. 

More  interesting  are  the  so-called  focal  lesions,  of  which  it 
may  be  said  that  certain  ones  are  caused  by  bacteria  and 
others  by  toxic  substances.  As  an  example  of  the  former,  a 
small  abscess  may  be  taken.  The  bacteria  which  are  most 
commonly  associated  with  this  pathological  process  are  cocci, 
which  grow  in  grape-like  clusters  presenting  often,  when  cul- 
tivated on  artificial  media,  a  golden-yellow  color,  whence  the 
name  **  Staphylococcus  pyogenes  aureus."      If  a  section   be 


6  BIOLOGICAL   LECTURES. 

made  through  such  an  abscess  (Fig.  i),  which  is  located,  as  so 
commonly  happens  in  experimental  cases,  in  the  kidney,  the 
following  arrangement  is  found.  The  central  dark  mass  repre- 
sents the  bacteria  which  have  been  transported  hither  by  the 
blood  current,  and  which  have  become  lodged  in  the  capillary 
vessels  of  the  part.  Having  found  here  conditions  favorable 
to  their  increase,  they  have  grown  from  a  microscopic  speck  to 
a  mass  large  enough  to  be  seen  with  the  naked  eye.  As  a 
result  of  their  presence,  the  surrounding  tissue  is  destroyed, 
the  destruction  being  recognizable  in  the  specimen  by  the 
absence  of  stainable  nuclei  in  this  part.  Outside  the  zone  of 
dead  tissue  is  another  in  which  the  cells  as  compared  with 
those  of  the  healthy  tissue  at  a  distance  are  greatly  increased 
in  number.  This  third  zone  is  the  area  of  leucocytic  infiltra- 
tion, the  infiltrating  cells  consisting  of  white  blood-corpuscles 
which  have  passed  out  of  the  vessels  to  accumulate  at  this  spot 
in  answer  to  what  is  conceived  to  be  a  chemical  attraction 
(chemotropism)  exerted  by  the  bacteria  and  dead  tissue.  The 
leucocytes  penetrate  as  far  as  possible  into  the  dead  tissue, 
and  become  arrested  as  soon  as  the  poisonous  products  of  the 
bacteria  are  present  in  quantities  sufficient  to  insure  their 
speedy  destruction.  Later  a  solvent  action  is  exerted  by  the 
bacteria  upon  the  tissues,  causing  them  to  liquefy,  and  con- 
verting the  contents  into  "pus,"  the  removal  of  which  leaves 
a  cavity  behind.^ 

Certain  bacteria  are  capable  of  exerting  an  injurious  effect 
upon  tissues  and  organs  of  the  animal  body  at  a  greater  dis- 
tance from  their  place  of  localization.  Thus,  although  the 
diphtheria  bacillus  often  remains  localized  in  the  throats  of 
persons  suffering  from  diphtheria,  yet  very  extensive  local 
lesions  are  found  in  the  near  and  remote  lymphatic  glands,  in 
the  spleen,  liver,  heart,  nerves,  and  other  organs.  These 
lesions  are  attributable  to  the  absorption  into  the  body  of  the 
toxalbumin,  elaborated   by  the  bacteria  in  the  throat.      It  is 

1  It  is  not  to  be  concluded  that  this  is  the  only  kind  of  lesion  produced  by 
bacteria.  It  is  a  common  one,  and  has  been  selected  for  that  reason,  and  also 
because,  as  far  as  known,  it  is  never  produced  by  the  action  of  the  toxic  products 
of  bacteria  alone. 


INFECTION  AND   INTOXICATION.  7 

indeed  possible  by  using  the  bodies  of  susceptible  guinea  pigs 
and  rabbits  to  show  that  identical  pathological  changes  can  be 
produced  by  inoculation  with  the  toxalbumin  alone.  A  closer 
study  of  the  lesions  shows  them  to  be  different  from  those 
caused  by  the  pus-producing  cocci.  Such  a  lesion  in  the  liver 
of  the  guinea  pig,  resulting  from  diphtheria  intoxication,  is 
shown  in  Fig.  2.  Note  here  that  a  destruction  of  cells  has 
taken  place,  but  that  no  bacteria  are  to  be  seen  in  the  neighbor- 
hood of  the  dead  cells.  The  cells  themselves  present  a  different 
appearance  from  those  seen  in  the  kidney  abscess.  Individu- 
ally they  are  better  preserved  ;  their  outlines  are  sharper,  and 
they  are  more  easily  made  out  than  the  normal  cells.  Examined 
in  the  fresh  state,  in  physiological  salt  solution,  they  present  a 
characteristic  glassy  appearance,  whence  the  term  "hyaline," 
which  is  often  applied  to  them.  That  they  are  necrotic  is 
shown  not  only  by  the  behavior  of  their  protoplasm  in  the 
presence  of  staining  agents,  but  also  by  the  absence  of  normal 
nuclei  in  them.  For  the  most  part,  the  nuclei  have  entirely 
disappeared,  but  here  and  there  a  shrunken  one  can  be  seen, 
and  occasionally  small  pigmented  fragments  are  still  preserved. 
The  intensity  of  the  process  evidently  grows  less  as  one  pro- 
ceeds from  the  center  to  the  periphery  of  such  a  focus,  and  at 
the  extreme  edge  a  variable  number  of  leucocytes  are  encoun- 
tered. They  are  never  accumulated  in  quantities,  such  as  are 
seen  in  abscess  formation,  and  such  a  lesion  shows  no  tendency 
to  undergo  softening  with  the  production  of  an  abscess  or 
cavity.^ 

With  respect  to  the  toxalbumins  which  are  derived  from  the 
higher  plants  (ricin,  abrin),  I  have  found  that  the  pathological 
lesions  which  they  cause  are  similar,  if  not  identical,  with  those 
produced  by  the  toxalbumins  of  bacterial  origin. 

Besides  the  toxins  of  vegetable  origin,  toxic  proteid  sub- 
stances, some  of  which  are  of  great  potency,  are  yielded  by  the 
animal  kingdom.     Among  these  have  already  been  mentioned 

1  When  it  is  considered  that  these  toxins  are  soluble  substances,  and  pre- 
sumably in  perfect  solution  in  the  body  fluids,  the  explanation  of  their  tendency 
to  produce  focal  effects  is  not  at  once  evident.  Several  hypotheses  have  been 
advanced  to  account  for  this  phenomenon.  See  "The  Pathological  Changes 
Caused  by  Certain  So-called  Toxalbumins."     Medical  News,  Phila.,  Aug.  4,  1894. 


8  BIOLOGICAL   LECTURES. 

the  toxic  constituents  of  snake  venom  and  the  blood  of  certain 
animals.  The  poisonous  effects  of  snake  venom  are  familiar 
to  you ;  but  it  is  less  generally  known  that  the  blood  of  one 
species  of  animal,  freed  from  its  corpuscular  elements,  may 
exhibit  poisonous  properties  when  introduced  in  sufficient 
amounts  into  an  animal  of  a  different  species.  Thus  the  blood 
serum  of  human  beings,  and  of  the  dog,  is  highly  poisonous  to 
the  rabbit,  and  that  of  the  lamb  to  human  beings. 

In  the  course  of  my  studies  in  this  direction,  I  have  been 
able  to  show  that  the  injurious  effects  which  the  blood  of  one 
animal  produces  in  another  is  due  to  the  toxic  substances  con- 
tained in  the  foreign  blood,  and  not  alone  to  the  destruction  of 
the  blood-corpuscles  of  the  host  which  commonly  ensues.  This 
latter  phenomenon  is  spoken  of  as  the  globulicidal  in  contra- 
distinction to  the  toxicidal  effects  of  the  foreign  serum,  and 
when  the  amount  of  foreign  serum  introduced  into  a  susceptible 
animal  is  very  large,  the  destruction  of  corpuscular  elements 
may  be  great  enough  to  cause  immediate  death.  The  toxicidal 
effect  is  produced  much  more  slowly.  The  toxic  constituents 
of  the  blood  serum  obtained  either  from  the  dog  or  from  human 
beings  bring  about  in  the  tissues  of  the  rabbit  changes  similar 
to  those  caused  by  the  vegetable  toxalbumins  which  have  been 
considered. 

Having  now  seen  that  these  agents  of  intoxication,  whether 
derived  from  animal  forms  of  low  or  high  position,  or  from 
vegetable  life  high  or  low  in  point  of  organization,  possess 
certain  features  in  common  and  produce  similar  pathological 
effects  when  tested  upon  susceptible  animals,  it  will  be  of 
interest  to  extend  a  little  further  our  inquiry  into  their 
properties. 

Among  the  most  interesting  of  these  from  a  theoretical,  and 
of  the  greatest  significance  from  a  practical  standpoint,  are  the 
effects  of  small  and  repeated  doses  of  these  substances.  The 
facts  elicited  by  the  study  of  the  effects  produced  by  these 
bodies  when  introduced  into  certain  animals  in  this  way  have 
an  important  bearing  upon  the  questions  of  insusceptibility  to 
disease  in  general,  and  are  included  in  the  subject  matter  of 
immunity. 


INFECTION  AND   INTOXICATION.  9 

The  production  of  immunity  to  many  bacteria  or  their  pro- 
ducts is  associated  with  the  formation  in  the  animal  thus 
protected  of  certain  antidotal  substances  which  appear  in  the 
body  fluids.  It  has  been  shown  that  a  similar  immunity  for 
ricin  and  abrin  can  be  induced,  and  more  recently  the  same 
has  been  proved  for  snake  venom.  In  these  instances  the 
insusceptibility  to  the  actions  of  the  toxic  agents  is  associated 
with  the  appearance  in  the  blood  of  the  treated  animals  of 
antidotal  bodies  capable  of  affording  protection  from  these 
toxic  proteids.  In  this  connection,  I  have  been  able  to  show 
that  by  the  exhibition  of  repeated  small  doses,  rabbits,  other- 
wise highly  susceptible,  can  be  made  quite  resistent  to  the 
blood  serum  of  the  dog. 

The  foregoing  considerations  teach  that,  in  the  study  of  the 
causation  of  disease,  a  widening  knowledge  is  enabling  us  to 
appreciate  how  much  is  due  to  the  actions  of  the  living  para- 
sitic agents  themselves,  and  how  much  to  toxic  substances 
derived  from  these  and  from  other  sources.  The  importance 
of  agents  of  intoxication  is  becoming  more  and  more  impressed 
upon  us;  and  when  we  reflect  that  their  distribution  is  co- 
extensive with  organized  nature  itself,  and  that  they  are 
present  in  the  most  vital  of  our  body  constituents,  we  begin  to 
see,  if  indeed  only  faintly,  what  consequences  their  presence 
may  entail. 

I  would  bring  these  remarks  to  a  close  by  begging  you  not 
to  forget  that  although  much  has  been  written  upon  the  disease- 
producing  micro-organisms,  not  a  small  chapter  might  be  added 
upon  those  which  are  friendly  in  their  nature.  When  you 
consider  that  the  phenomena  of  decomposition  and  putrefaction 
are  executed  through  their  efforts,  that  the  restoration  of  the 
soil,  and  the  fitting  of  it  for  the  growth  of  the  higher  plants, 
is  effected  by  a  special  group  of  bacteria,  you  will  appreciate 
the  fact  that  life  on  this  globe  would  be  impossible  for  the 
higher  living  forms  could  these  lowly  ones  be  perchance 
exterminated. 

Furthermore,  there  are  defences  set  up  everywhere  in  the 
animal  body  through  which  the  invasion  of  these  noxious  para- 
sites is  resisted.     Those  parts  most  exposed  to  their  action 


lO  BIOLOGICAL   LECTURES. 

are  either  covered  by  a  dense  and  relatively  impenetrable  mem- 
brane, or  if  protected  by  a  barrier  less  secure,  are  bathed  with 
fluids  at  once  injurious  to  them,  and  offering  mechanical 
obstacles  to  their  settlement.  Thus  for  the  exterior  of  the 
body  we  have  as  a  rampart,  the  skin,  and  for  each  orifice  its 
mucous  surface  with  its  own  peculiar  secretion.  Even  should 
the  parasite  be  able  to  pass  beyond  these  outposts,  its  fate  is 
still  insecure,  for  the  lymphatic  tissues  stand  as  a  closed  gate- 
way to  oppose  its  further  progress  ;  and  beyond  these  again 
are  forces  still  more  impregnable,  —  the  body  fluids  and  cells, 
which  are  capable  of  destroying  large  numbers  of  bacteria, 
and  probably  no  inconsiderable  quantities  also  of  their  toxic 
products. 


SECOND    LECTURE. 


IMMUNITY. 

BY   GEORGE   M.    STERNBERG,   M.D.,   LL.D. 
(Surgeon-General  U.  S.  Army,  Washington,  D.  C.) 

The  resisting  power,  natural  or  acquired,  which  living 
animals  possess  against  invasion  by  pathogenic  micro-organ- 
isms is  commonly  spoken  of  as  **  immunity."  But  we  might 
include  in  our  definition  of  the  term,  used  in  the  biological 
sense  which  we  shall  attach  to  it  in  the  present  lecture,  the 
more  general  resisting  power  which  living  animals  possess 
against  saprophytic  bacteria.  It  is  hardly  necessary  to  call 
attention  to  the  fact  that,  under  suitable  conditions  as  to  tem- 
perature and  moisture,  dead  animal  tissues  undergo  putrefac- 
tive decomposition, — i.e.  are  invaded  by  saprophytic  bacteria, — 
while  healthy,  living  animals  resist  such  invasion.  This  more 
general  immunity  appears  to  be  due  to  causes  which  are  the 
same  or  similar  to  those  which  enable  insusceptible  animals 
to  resist  invasion  by  pathogenic  bacteria.  There  is  also  an 
immunity,  which  the  Germans  designate  *^ giftfestigtmg,''  which 
is  manifested  by  an  increased  resisting  power  to  the  toxic 
action  of  the  chemical  products  of  pathogenic  bacteria,  and 
which  may  be  established  by  introducing  these  toxic  substances 
into  susceptible  animals  quite  independently  of  the  micro- 
organisms which  produce  them  —  inoculations  with  filtered 
or  sterilized  cultures.  This  corresponds  with  the  acquired 
immunity  which  has  been  shown  to  result  from  the  inoculation 
of  susceptible  animals  with  non-lethal  doses  of  certain  toxic 
albuminous  substances  of  animal  and  vegetable  origin,  —  snake 
poison,  abrin,  ricin,  etc. 


12  BIOLOGICAL  LECTURES. 

By  ''natural  immunity"  we  mean  the  insusceptibility  which 
certain  species  or  certain  individuals  have  against  infection  by 
certain  pathogenic  bacteria.  "  Acquired  immunity "  is  the 
resisting  power  which  results,  in  originally  susceptible  animals, 
from  a  non-fatal  attack  of  an  infectious  disease,  or  from  pro- 
tective inoculations  with  "attenuated"  or  filtered  cultures  of 
pathogenic  bacteria. 

As  is  well  known,  certain  infectious  diseases  are  peculiar  to 
man,  certain  others  to  one  or  more  species  of  lower  animals, 
and  others  still  may  be  transmitted  from  man  to  certain  lower 
animals,  or  vice  versa.  Thus  typhoid  fever,  yellow  fever, 
cholera,  measles,  etc.,  are  infectious  diseases  of  man,  and 
during  their  epidemic  prevalence  the  lower  animals  show  no 
evidence  of  susceptibility  to  infection.  On  the  other  hand, 
Texas  fever  and  infectious  pleuropneumonia,  which  are  very 
fatal  to  cattle,  hog  cholera  and  swine  plague,  chicken  cholera, 
etc.,  are  never  communicated  to  those  who  care  for  the  infected 
animals  ;  in  other  words,  man  has  a  natural  immunity  against 
these  diseases.  Again,  certain  infectious  diseases  are  common 
to  man  and  to  certain  species  of  the  lower  animals.  Thus, 
tuberculosis  may  be  transmitted  to  monkeys,  to  cattle,  rabbits, 
guinea  pigs,  and  fowls  ;  carnivorous  animals  in  confinement, 
also,  sometimes  succumb  to  tubercular  infection.  Anthrax 
is  fatal  to  cattle,  sheep,  and  small  herbivorous  animals,  and 
may  be  transmitted  to  man  by  inoculation,  or  by  the  introduc- 
tion of  dry  spores  into  the  respiratory  passages  —  '*  wool- 
sorter's  disease."  Diphtheria  may  be  transmitted  to  cats  and 
fowls,  and  cultures  of  the  diphtheria  bacillus  are  extremely 
pathogenic  for  the  guinea  pig.  Glanders,  which  is  a  disease  of 
the  equine  genus,  may  be  transmitted  to  man,  to  the  guinea  pig, 
and  to  the  field  mouse  ;  but  house  mice  have  a  natural  immunity 
against  infection  by  this  bacillus.  On  the  other  hand,  field 
mice  and  guinea  pigs  are  not  susceptible  to  infection  by  the 
Bacillus  erysipelatus  suis,  which  is  very  fatal  to  house  mice, 
white  mice,  rabbits,  swine,  sparrows,  and  pigeons.  There  are 
also  differences  in  susceptibility  to  various  infectious  diseases 
among  different  races  of  the  same  species.  Thus  the  Algerian 
sheep  has  an  immunity  against   anthrax  ;    Texas  cattle,  as  a 


IMMUNITY. 


13 


rule,  do  not  succumb  to  Texas  fever,  which  is  very  fatal  to 
northern  cattle ;  yellow  fever  is  much  less  fatal  to  the  negro 
than  to  the  white  race ;  the  negro  also  resists  malarial  infection 
better  than  the  white.  In  general,  carnivorous  animals  have 
but  slight  susceptibility  to  the  various  forms  of  infectious 
septicaemia  which  are  fatal  to  the  herbivora.  The  introduction 
beneath  the  skin  of  a  mouse  or  a  rabbit  of  a  little  putrefying 
flesh  infusion  frequently  gives  rise  to  a  fatal  septicaemia,  due 
to  the  presence  of  one  or  more  species  of  bacteria  pathogenic 
for  these  animals,  but  harmless  for  the  carnivora  which  prey 
upon  them.  Were  this  otherwise,  the  carnivora  would  be 
destroyed  by  wounds  inflicted  in  their  fights  over  animals 
which  had  died  of  infectious  diseases  or  which  were  in  a  state 
of  putrefaction.  It  appears  probable  that  the  immunity  of  the 
carnivora  to  the  infectious  septicaemias  referred  to  has  been 
acquired  in  process  of  time  by  natural  selection  —  survival  of 
the  fittest. 

Besides  the  race  immunity  referred  to,  we  have  differences 
in  the  degree  of  susceptibility  to  various  infectious  diseases  in 
individuals  of  the  same  race.  Some  individuals  or  families 
have  manifestly  a  special  susceptibility  to  tubercular  infection ; 
others  are  especially  subject  to  contract  smallpox,  as  shown  by 
the  occurrence  of  two  or  more  attacks  in  the  same  individual. 
Susceptibility  also  depends  to  some  extent  upon  age.  The 
young  are  especially  susceptible  to  scarlet  fever,  whooping 
cough,  and  diphtheria.  In  the  lower  animals,  we  find  that  an 
"attenuated  virus"  which  will  not  kill  an  adult  of  a  susceptible 
species  may  prove  fatal  to  a  very  young  animal  of  the  same 
species. 

Immunity,  whether  natural  or  acquired,  in  many  cases  has 
only  a  relative  value,  and  may  be  overcome  by  an  excessive 
dose  or  by  unusual  virulence  of  the  infectious  material.  This 
is  true,  for  example,  of  the  natural  immunity  of  the  Algerian 
race  of  sheep  as  regards  anthrax,  of  the  acquired  immunity 
resulting  from  vaccination  against  smallpox,  etc.  But  it  does 
not  apply  in  the  case  of  animals  which  have  a  complete  natural 
immunity  for  infectious  diseases  peculiar  to  other  species. 
Thus  man  never  contracts  swine  plague  or  infectious  pleuro- 


14  BIOLOGICAL   LECTURES. 

pneumonia  under  any  circumstances,  and  domestic  animals 
never  contract  yellow  fever  or  cholera  during  the  epidemic 
prevalence  of  these  diseases. 

The  relative  immunity,  natural  or  acquired,  to  diseases  which 
are  not  strictly  limited  to  a  single  species,  may  often  be  over- 
come by  various  agencies  acting  upon  the  individual  exposed 
to  infection.  Thus  Arloing  was  able  to  induce  symptomatic 
anthrax  in  animals  naturally  immune  for  this  disease  by  mix- 
ing with  his  cultures  various  chemical  substances,  such  as  car- 
bolic acid,  pyrogallic  acid,  and  especially  lactic  acid  (twenty 
per  cent).  Leo  has  shown  that  white  mice,  which  are  not 
subject  to  the  pathogenic  action  of  the  glanders  bacillus,  may 
be  rendered  susceptible  by  feeding  them  for  some  time  upon 
phloridzin,  which  gives  rise  to  an  artificial  diabetes,  and  causes 
the  tissues  to  become  impregnated  with  sugar.  Behring 
claims  to  have  demonstrated  by  experiment  that  white  rats 
lose  their  immunity  for  anthrax  when  fed  for  some  time  upon 
an  exclusively  vegetable  diet,  or  when  phosphate  of  lime  is 
added  to  their  food ;  and  he  has  suggested  that  the  immunity 
of  these  animals  may  be  due  to  the  highly  alkaline  reaction  of 
their  blood  and  tissue  juices.  Nocard  and  Roux  found  by 
experiment  that  an  attenuated  culture  of  the  anthrax  bacillus, 
which  was  not  fatal  to  guinea  pigs,  killed  these  animals  when 
injected  into  the  muscles  of  the  thigh  after  they  had  been 
bruised  by  mechanical  violence.  Abarrin  and  Roger  found 
that  white  rats,  which  are  not  susceptible  to  anthrax,  became 
infected  and  frequently  died  if  they  were  exhausted,  previous 
to  inoculation,  by  being  compelled  to  turn  a  revolving  wheel 
for  a  considerable  time.  Pasteur  found  that  fowls,  which  have 
a  natural  immunity  against  anthrax,  become  infected  and  perish 
if  they  are  subjected  to  artificial  refrigeration  after  inoculation. 
This  has  been  confirmed  by  the  more  recent  experiments  of 
Wagner  (1891).  According  to  Canalis  and  Morpurgo,  pigeons 
which  are  enfeebled  by  inanition  easily  contract  anthrax  as 
a  result  of  inoculation.  Arloing  states  that  sheep  which  have 
been  freely  bled  contract  anthrax  more  easily  than  others  ;  and 
Serafini  found  that  when  dogs  were  freely  bled,  the  bacillus  of 
Friedlander,  injected  into  the  trachea  or  the  pleural  cavity. 


IMMUNITY. 


15 


entered,  and  apparently  multiplied  to  some  extent  in  the 
blood,  whereas  without  such  previous  bleeding  they  were  not 
to  be  found  in  the  circulating  fluid.  Certain  anaesthetic 
agents  have  also  been  shown  to  produce  a  similar  result. 
Platania  communicated  anthrax  to  immune  animals  —  dogs, 
frogs,  pigeons  —  by  bringing  them  under  the  influence  of 
curare,  chloral,  or  alcohol ;  and  Wagner  obtained  similar  re- 
sults in  his  experiments  upon  pigeons  to  which  he  had  admin- 
istered chloral.  In  man,  clinical  experience  shows  that  those 
who  are  addicted  to  the  excessive  use  of  alcohol  are  especially 
liable  to  contract  certain  infectious  diseases,  —  pneumonia, 
erysipelas,  yellow  fever,  etc. 

The  pathogenic  potency  of  known  disease  germs  varies  as 
widely  as  does  the  susceptibility  of  individuals  to  their  specific 
action.  In  general  it  may  be  said  that  the  more  recently  the 
germ  comes  from  a  developed  case  of  the  disease  to  which  it 
gives  rise,  the  more  virulent  it  is,  and  the  longer  it  has  been 
cultivated  outside  of  the  animal  body,  the  more  attenuated  is 
its  pathogenic  power.  Thus,  when  the  discharges  of  a  typhoid- 
fever  patient  find  their  way  directly  to  a  water-supply  of  limited 
amount,  a  large  proportion  of  those  who  drink  the  water  are 
likely  to  be  attacked  ;  but  when  a  considerable  interval  of  time 
has  elapsed  since  the  contamination  occurred,  although  the 
germs  may  still  be  present,  the  liability  to  attack  is  much  less, 
on  account  of  diminished  pathogenic  virulence. 

What  has  been  said  thus  far  indicates  that  infection  depends 
{a)  upon  the  susceptibility  of  the  individual  (predisposition), 
{b)  upon  the  virulence  of  the  infectious  agent,  and  {c)  upon 
the  quantity  introduced  to  a  vulnerable  point,  —  e.g.  beneath 
the  skin  by  inoculation  or  through  an  accidental  wound  in 
anthrax  and  other  forms  of  septicaemia,  into  the  alimentary 
canal  in  typhoid  fever  and  cholera,  or  into  the  respiratory  pas- 
sages in  diphtheria,  influenza,  pneumonia,  and  pulmonary  tuber- 
culosis. Still  another  factor  may  be  called  into  play.  In 
addition  to  the  specific  cause  or  germ,  and  the  natural  or 
acquired  (by  various  depressing  agencies  referred  to)  predis- 
position, a  direct  exciting  cause  may  be  necessary  to  establish 
a  localized  infectious  process.     Thus,  catching  cold  may  be  the 


1 6  BIOLOGICAL   LECTURES. 

exciting  cause  which  develops  an  attack  of  pneumonia  or 
influenza  or  tuberculosis  in  an  individual  having  a  predisposi- 
tion to  these  diseases,  —  the  specific  cause  being  present ;  or 
indigestible  food  in  the  primae  viae  may  be  the  exciting  cause 
of  an  attack  of  cholera ;  or  the  irritation  resulting  from  breath- 
ing an  atmosphere  loaded  with  dust  may  give  rise  to  tubercular 
infection.  Again,  bruising  of  the  tissues  may  give  rise  to  an 
abscess  or  a  carbuncle  in  an  individual  whosQ  vital  resisting 
power  is  below  par,  the  specific  agents  of  such  local  infections 
(the  pus  cocci)  being  widely  distributed  and  frequently  found 
on  the  surface  of  the  body  and  upon  exposed  mucous  mem- 
branes in  healthy  individuals. 

A  non-fatal  attack  of  an  infectious  malady,  as  a  rule,  is 
followed  by  a  relative  immunity  of  longer  or  shorter  duration. 
In  smallpox,  scarlet  fever,  measles,  yellow  fever,  typhoid  fever, 
and  certain  other  diseases  of  man  one  attack  usually  protects 
during  the  life  of  the  individual;  but  exceptions  to  this  rule  are 
not  rare,  especially  in  the  case  of  smallpox.  In  pneumonia, 
diphtheria,  influenza,  and  cholera  second  attacks  are  frequent ; 
and  while  a  relative  degree  of  immunity  is  no  doubt  acquired 
as  a  result  of  an  attack,  this  is  of  brief  duration. 

The  production  of  immunity  by  protective  inoculations  was 
for  a  long  time  limited  to  a  single  disease,  —  smallpox. 
Inoculations  with  virus,  obtained  from  a  pustule  on  a  smallpox 
patient,  were  extensively  practised  before  the  discovery  of 
vaccination  by  Jenner.  These  inoculations  gave  rise  to  a  mild 
attack  of  the  disease,  followed  by  immunity,  which  was  appar- 
ently as  complete  as  that  following  a  more  severe  attack  con- 
tracted in  the  usual  way.  This  method  seems  to  have  been 
practised  by  eastern  nations  long  before  it  was  introduced  into 
Europe.  It  was  extensively  employed  in  Turkey  early  in  the 
eighteenth  century,  and  was  introduced  into  England  through 
the  influence  of  Lady  Mary  Wortley  Montagu.  No  doubt  the 
mortality  from  smallpox  was  greatly  diminished  by  these 
inoculations  ;  but  they  were  attended  by  the  disadvantage  that 
the  disease  was  propagated  by  them,  inasmuch  as  inoculated 
individuals  became  a  source  of  infection  for  others.  Inocula- 
tion was  still  practised  in  England  for  some  time  after  the 


IMMUNITY,  1 7 

demonstration  of  the  protective  value  of  vaccination,  but  in 
1840  it  was  prohibited  by  an  act  of  Parliament. 

There  is  some  evidence  that  vaccination  as  a  protection 
against  smallpox  was  practised  to  a  limited  extent  prior  to  the 
time  of  Jenner.  Thus  Von  Humboldt  has  stated  that  it  was 
known  at  an  early  period  to  the  Mexicans.  But  its  introduc- 
tion as  a  reliable  method  of  protecting  against  smallpox  is  due 
to  the  patient  researches  of  the  renowned  English  physician, 
whose  attention  was  first  attracted  to  the  subject  in  1768, 
although  it  was  not  until  1796  that  he  made  his  first  vaccina- 
tion in  the  human  subject.  His  first  public  institution  for  the 
practice  of  vaccination  was  established  in  1 799,  and  the  follow- 
ing year  the  practice  was  introduced  into  France,  Germany, 
and  the  United  States. 

In  the  infectious  disease  of  cattle  known  as  pleuropneumonia, 
protective  inoculations  were  successfully  made  some  time 
before  the  demonstration  by  Pasteur  of  the  efficacy  of  such 
inoculations  in  anthrax  and  chicken  cholera  (1880).  Various 
methods  have  been  employed.  Thus  Willems  states  that  the 
natives  of  the  banks  of  the  Zambeze  cause  animals  to  swallow 
a  certain  quantity  of  the  liquid  from  the  pleural  cavity  of  an 
animal  recently  dead,  and  thus  give  them  immunity.  The 
virus  has  been  injected  into  the  circulation  by  some  experi- 
menters, and  others  have  proposed  to  attenuate  it  by  heat. 
But  the  method  which  has  been  most  extensively  employed  is 
that  discovered  by  the  Dutch  settlers  at  the  Cape  of  Good 
Hope  (the  Boers),  and  consists  in  inoculating  animals  in  the 
tail  with  serum  from  the  lungs  of  an  animal  recently  dead,  or 
with  a  virus  obtained  from  the  tumefaction  produced  by  such 
an  inoculation  in  the  tail.  This  secondary  virus  was  very 
extensively  used  by  Lenglen,  a  veterinarian  at  Arras,  who 
communicated  his  results  to  the  Academy  of  Science  at  Paris, 
in  April,  1863,  and  Willems  says,  in  his  last  published  commu- 
nication, that  this  is  the  method  which  he  prefers.  It  is  also 
the  method  most  extensively  employed  in  Australia,  into  which 
country  infectious  pleuropneumonia  was  introduced  in  1858. 

Toussaint,  a  pioneer  in  researches  relating  to  protective 
inoculations,  has  a  short  paper  in  the  Comptes-Rendiis  of  the 


1 8  BIOLOGICAL   LECTURERS. 

French  Academy  of  Sciences  of  July  12,  1880,  entitled 
"  Immunity  from  Anthrax  ('  charbon ')  Acquired  as  a  Result 
of  Protective  Inoculations." 

In  this  paper  he  announces  his  discovery  of  the  important 
fact  that  the  anthrax  bacillus  does  not  form  spores  in  the  tis- 
sues or  liquids  of  the  body  of  an  infected  animal,  but  multiplies 
alone  by  binary  division,  —  "sa  multiplication  se  fait  toujours 
par  une  division  du  mycelium." 

In  the  same  communication  he  reports  his  success  in  con- 
ferring immunity  upon  five  sheep  by  means  of  protective 
inoculations,  and  also  upon  four  young  dogs.  We  must,  there- 
fore, accord  him  the  priority  in  the  publication  of  experimental 
data  demonstrating  the  practicability  of  accomplishing  this 
result. 

But  it  is  especially  to  the  experimental  researches  of  Pasteur 
that  we  are  indebted  for  the  development  of  practical  methods, 
which  have  been  extensively  employed  in  protecting  cattle, 
sheep,  and  swine  from  the  fatal  effects  of  various  infectious 
maladies,  and  man  from  hydrophobia  as  the  result  of  the  bite 
of  a  rabid  animal. 

Pasteur's  inoculations  are  made  with  an  "attenuated  virus," 
—  i.e.  with  a  culture  of  a  pathogenic  micro-organism  which  has 
a  diminished  degree  of  virulence  and  which  when  introduced 
into  a  susceptible  animal  induces  a  non-fatal  and  comparatively 
mild  attack. 

The  researches  of  Pasteur  and  of  his  followers  in  this  line  of 
investigation  show  that  pathogenic  virulence  may  be  attenuated 
by  prolonged  exposure  to  oxygen  ;  by  exposure  to  a  tempera- 
ture a  little  below  that  which  would  completely  destroy  vitality; 
by  the  action  of  certain  chemica4  agents ;  and  in  some  cases, 
by  passing  through  a  series  of  non-susceptible  animals. 

As  a  general  rule  pathogenic  virulence  is  increased  by  suc- 
cessive inoculations  in  susceptible  animals  and  diminished  by 
cultivating  the  pathogenic  micro-organism  in  artificial  media 
outside  of  the  animal  body  or  by  passing  it  through  animals 
having  but  slight  susceptibility  to  its  pathogenic  action.  As 
pathogenic  virulence  depends,  to  a  considerable  extent  at  least, 
upon    the    formation    of    toxic    substances    during    the  active 


IMMUNITY.  19 

development  of  the  pathogenic  micro-organism,  we  infer  that 
diminished  virulence  is  due  to  a  diminished  production  of  these 
toxic  substances. 

An  important  step  was  made  in  the  progress  of  our  knowl- 
edge in  this  field  of  research  when  it  was  shown  that  animals 
may  be  made  immune  against  certain  infectious  diseases  by 
inoculating  them  with  filtered  cultures,  containing  the  toxic 
substances  just  referred  to,  but  free  from  the  living  bacteria 
to  which  they  owe  their  origin.  The  first  satisfactory  experi- 
mental evidence  of  this  important  fact  was  obtained  by  Salmon 
and  Smith  in  1886.  These  bacteriologists  succeeded  in  pro- 
ducing an  immunity  in  pigeons  against  the  pathogenic  effects 
of  the  bacillus  of  hog  cholera,  which  is  very  fatal  to  these 
birds,  by  inoculating  them  with  sterilized  cultures  of  the 
bacillus  mentioned.  Similar  results  were  reported  by  Roux  in 
1888,  from  the  injection  into  susceptible  animals  of  sterilized 
cultures  of  the  anthrax  bacillus,  and  also  of  the  bacillus  of 
symptomatic  anthrax.  More  recently  (1890)  Behring  and 
Kitasato  have  shown  that  animals  may  be  made  immune 
against  the  pathogenic  action  of  the  bacillus  of  tetanus  or  the 
bacillus  of  diphtheria  by  the  injection  of  filtered,  germ-free 
cultures  of  these  bacilli.  Similar  results  have  been  obtained 
by  G.  and  F.  Klemperer  (1891),  in  experiments  upon  rabbits, 
with  filtered  cultures  of  the  micrococcus  of  croupous  pneu- 
monia. 

In  Pasteur's  protective  inoculations  against  hydrophobia  it 
is  probable  that  the  immunity  which  is  developed  after  infec- 
tion by  the  bite  of  a  rabid  animal  is  due  to  the  toxin  (toxal- 
bumin  t)  of  this  disease  present  in  the  emulsion  of  spinal  cord 
which  is  used  in  these  inoculations. 

There  is  also  some  evidence  to  show  that  a  certain  degree 
of  immunity  against  tuberculosis  may  be  produced  in  guinea 
pigs  by  injections  of  the  toxic  substances  developed  during  the 
growth  of  the  tubercle  bacillus,  —  Koch's  tuberculin. 


20  BIOLOGICAL  LECTURES. 


Explanation  of  Natural  Immunity. 

We  have  now  to  inquire  upon  what  the  natural  immunity 
depends  which  enables  the  healthy  animal  body  to  resist  inva- 
sion by  the  destructive  agents  referred  to. 

Phagocytosis.  —  In  my  chapter  on  "  Bacteria  in  Infectious 
Diseases,"  in  Bacteria^  published  in  the  spring  of  1884,  but 
placed  in  the  hands  of  the  publishers  in  1883,  I  say :  — 

**  It  may  be  that  the  true  explanation  of  the  immunity 
afforded  by  a  mild  attack  of  an  infectious  germ  disease  is  to 
be  found  in  an  acquired  tolerance  to  the  action  of  a  chemical 
poison  produced  by  the  micro-organism,  and  consequent  ability 
to  bring  the  resources  of  nature  to  bear  to  restrict  invasion  by 
the  parasite." 

In  the  same  chapter  the  resources  of  nature  supposed  to  be 
brought  to  bear  in  restricting  invasion  by  the  parasite  are 
referred  to  as  follows :  — 

*'  If  we  add  a  small  quantity  of  culture  fluid  containing  the 
bacteria  of  putrefaction  to  the  blood  of  an  animal  withdrawn 
from  the  circulation  into  a  proper  receptacle  and  maintained  in 
a  culture  oven  at  blood-heat,  we  will  find  that  these  bacteria 
multiply  abundantly,  and  evidence  of  putrefactive  decomposi- 
tion will  soon  be  perceived.  But  if  we  inject  a  like  quantity 
of  the  culture  fluid,  with  its  contained  bacteria,  into  the  cir- 
culation of  a  living  animal,  not  only  does  no  increase  and  no 
putrefactive  change  occur,  but  the  bacteria  introduced  quickly 
disappear,  and  at  the  end  of  an  hour  or  two  the  most  careful 
microscopical  examination  will  not  reveal  the  presence  of  a 
single  bacterium.  This  difference  we  ascribe  to  the  vital 
properties  of  the  fluid  as  contained  in  the  vessels  of  a  living 
animal,  and  it  seems  probable  that  the  little  masses  of  proto- 
plasm known  as  white  blood-corpuscles  are  the  essential  histo- 
logical elements  of  the  blood,  as  far  as  any  manifestation  of 
vitality  is  concerned.  The  writer  has  elsewhere  (1881)  sug- 
gested that  the  disappearance  of  the  bacteria  from  the  circtdatioiiy 
in  the  experiments  referred  tOy  may  be  effected  by  the  white 
corpuscles,  which,  it  is  well  known,  pick  up,  after  the  manner 


IMMUNITY.  2 1 

of  amoebae,  any  particles,  organic  or  inorganic,  which  come  in 
their  way.  And  it  requires  no  great  stretch  of  credulity  to 
believe  that  they  may^  like  an  amceba^  digest  and  assimilate  the 
protoplasm  of  the  captured  bacterium^  thus  putting  an  end  to  the 
possibility  of  its  doing  any  harm,. 

**  In  the  case  of  a  pathogenic  organism  we  may  imagine 
that,  when  captured  in  this  way,  it  may  share  a  like  fate  if  the 
captor  is  not  paralyzed  by  some  potent  poison  evolved  by  it,  or 
overwhelmed  by  its  superior  vigor  and  rapid  multiplication. 
In  the  latter  event  the  active  career  of  our  conservative  white 
corpuscles  would  be  quickly  terminated  and  its  protoplasm 
would  serve  as  food  for  the  enemy.  It  is  evident  that  in  a 
contest  of  this  kind  the  balance  of  power  would  depend  upon 
circumstances  relating  to  the  inherited  vital  characteristics  of 
the  invading  parasite  and  of  the  invaded  leucocyte." 

This  explanation  is  now  very  commonly  spoken  of  as  the 
"  Metschnikoff  theory,"  although,  as  shown  by  the  above 
quotations,  it  was  clearly  stated  by  the  writer  several  years 
(1881)  before  Metschnikoff's  first  paper  (1884)  was  published. 
Metschnikoff  has,  however,  been  the  principal  defender  of  this 
explanation  of  acquired  immunity,  and  has  made  extensive 
and  painstaking  researches,  as  a  result  of  which  many  facts 
have  been  brought  to  light  which  appear  to  give  support  to 
the  present  writer's  hypothesis,  —  the  so-called  Metschnikoff 
theory. 

The  time  at  my  disposal  will  not  permit  me  to  review  the 
experimental  evidence  for  and  against  the  view  that  phagocytosis 
is  the  principal  factor  in  protecting  animals  from  invasion  by 
pathogenic  bacteria.  The  conclusion  which  I  have  reached  is 
stated  in  my  recently  published  work  on  Immunity^  Protective 
Inoculation^  and  Serum-  Therapy  as  follows  :  — 

"The  experimental  evidence  submitted,  considered  in  con- 
nection with  the  extensive  literature  relating  to  'phagocytosis,' 
leads  us  to  the  conclusion  that  natural  immunity  is  due  to  a 
germicidal  substance  present  in  the  blood-serum  which  has  its 
origin  (chiefly,  at  least)  in  the  leucocytes,  and  is  soluble  only 
in  an  alkaline  medium  ;  and  that  local  infection  is  usually 
resisted  by  an   afflux  of  leucocytes  to  the  point  of  invasion, 


22  BIOLOGICAL   LECTURES. 

but  that  phagocytosis  is  a  factor  of  secondary  importance  in 
resisting  parasitic  invasion  ;  also  that  general  infection,  at 
least  in  some  infectious  diseases,  is  resisted,  and  in  non-fatal 
cases  overcome,  by  an  increase  in  the  number  of  leucocytes 
and  in  the  alkalinity  of  the  blood-serum,  —  which  favors  solu- 
tion of  the  germicidal  proteids  contained  in  the  polynuclear 
leucocytes," 

Recent  researches  indicate  that  the  principal  factor  in  the 
production  of  acquired  immunity  is  the  presence  in  the  blood 
of  the  immune  animal  of  some  substance  capable  of  neutral- 
izing the  toxic  products  of  the  particular  pathogenic  micro- 
organism against  which  immunity  exists,  or  of  destroying  the 
"  germ  "  itself. 

These  substances  are  called  antitoxins.  As  pointed  out  by 
Buchner  in  a  recent  paper,  the  antitoxins  differ  essentially 
from  the  so-called  alexins,  to  which  natural  immunity  is 
ascribed.  The  alexins  are  characterized  by  their  germicidal 
and  globulicidal  action  (they  destroy  both  the  red  corpuscles 
and  the  leucocytes  of  animals  belonging  to  a  different  species 
from  that  from  which  they  have  been  obtained),  and  by  their 
coagulability  and  instability  —  destroyed  by  sunlight  and  by  a 
temperature  of  50°  to  55°  C.  On  the  other  hand,  the  anti- 
toxins best  known  (diphtheria  and  tetanus)  have  no  germicidal 
or  globulicidal  action ;  they  resist  the  action  of  sunlight  and 
require  a  temperature  of  70°  to  80°  C.  for  their  destruction. 

Our  knowledge  of  the  antitoxins  dates  from  the  experiments 
made  in  the  Hygienic  Institute  of  Tokio,  by  Ogata  and 
Jasuhara,  in  1890.  These  bacteriologists  discovered  the  im- 
portant fact  that  the  blood  of  an  animal  immune  against  anthrax 
contains  some  substance  which  neutralizes  the  toxic  products 
of  the  anthrax  bacillus.  When  cultures  were  made  in  the 
blood  of  dogs,  frogs,  or  of  white  rats,  which  animals  have  a 
natural  immunity  against  anthrax,  they  were  found  not  to  kill 
mice  inoculated  with  them.  Further  experiments  showed  that 
mice  inoculated  with  virulent  anthrax  cultures  did  not  succumb 
to  anthrax  septicaemia  if  they  received  at  the  same  time  a  sub- 
cutaneous injection  of  the  blood  of  an  immune  animal.  Further, 
it  was  found  that  mice  which  had  survived  anthrax  infection  as 


IMMUNITY.  23 

a  result  of  this  treatment  were  immune  at  a  later  date  (after 
several  weeks),  when  inoculated  with  a  virulent  culture  of  the 
anthrax  bacillus.  In  the  same  year  (1890)  Behring  and  Kita- 
sato  discovered  that  the  blood  of  an  animal  which  has  an 
acquired  immunity  against  tetanus  or  diphtheria,  when  added 
to  a  virulent  culture  of  one  or  the  other  of  these  bacilli, 
neutralizes  the  pathogenic  power  of  such  cultures,  as  shown 
by  inoculation  into  susceptible  animals  ;  and  also  that  cultures 
from  which  the  bacilli  have  been  removed  by  filtration,  and 
which  kill  susceptible  animals  in  very  small  amounts,  have 
their  toxic  potency  destroyed  by  adding  to  them  the  blood  of 
an  immune  animal,  which  is  thus  directly  proved  to  contain  an 
antitoxin, —  which  comparative  experiments  show  not  to  be 
present  in  the  blood  of  non-immune  animals.  In  the  experi- 
ments of  Behring  and  Kitasato  referred  to,  it  was  found  that 
5  c.c.  of  serum  from  the  blood  of  an  immune  rabbit,  mixed  with 
I  c.c.  of  a  virulent  filtrate  of  the  tetanus  bacillus,  and  allowed 
to  stand  for  twenty -four  hours,  completely  neutralized  its  toxic 
power,  as  shown  by  inoculations  in  mice :  0.2  c.c.  of  this 
mixture  injected  into  a  mouse  was  without  effect,  while 
0.000 1  c.c.  of  the  filtrate,  without  such  admixture,  was  infallibly 
fatal  to  mice.  The  mice  inoculated  with  this  mixture  remained 
immune  for  forty  or  fifty  days,  after  which  they  gradually  lost 
their  immunity.  The  blood  or  serum  from  an  immune  rabbit, 
when  preserved  in  a  dark,  cool  place,  retained  its  power  of 
neutralizing  the  tetanus  toxalbumin  for  about  a  week,  after 
which  time  it  gradually  lost  this  power.  Behring  and  Kitasato 
have  also  shown  that  the  serum  of  a  diphtheria-immune  rabbit 
destroys  the  potent  toxalbumin  in  diphtheria  cultures.  It  does 
not,  however,  possess  any  germicidal  power  against  the  diph- 
theria bacillus. 

In  1 89 1  G.  and  F.  Klemperer  published  an  important 
memoir,  in  which  they  give  an  account  of  their  researches 
relating  to  the  question  of  immunity,  etc.,  in  animals  subject 
to  the  form  of  septicaemia  produced  by  the  micrococcus  of 
croupous  pneumonia.  They  were  able  to  produce  immunity  in 
susceptible  animals  by  introducing  into  their  bodies  filtered 
cultures  of  this  micrococcus,  and  proved  by  experiment  that 


24  BIOLOGICAL   LECTURES. 

this  immunity  had  a  duration  of  at  least  six  months.  They 
also  arrived  at  the  conclusion  that  the  immunity  induced  by 
injecting  filtered  cultures  into  susceptible  animals  is  due  to  the 
production  of  an  antitoxin  in  the  body  of  the  animal. 

Brieger,  Kitasato,  and  Wassermann  have  reported  (1892) 
their  success  in  conferring  immunity  upon  guinea  pigs  against 
the  pathogenic  action  of  the  cholera  spirillum.  They  found 
that  attenuated  cultures  suitable  for  use  as  "vaccines"  could 
be  obtained  by  cultivating  the  spirillum  in  bouillon  made  from 
the  thymus  gland  of  the  calf,  by  which  means  they  have  also 
obtained  attenuated  cultures  of  the  bacillus  of  diphtheria,  the 
bacillus  of  typhoid  fever,  the  bacillus  of  tetanus  and  the  strep- 
tococcus of  erysipelas.  Guinea  pigs  inoculated  with  a  culture 
in  thymus  bouillon,  which  had  been  subjected  to  a  temperature 
of  65°  C.  for  fifteen  minutes,  were  found  after  twenty-four 
hours  to  be  immune  against  virulent  cultures  in  twice  the 
amount  which  would  otherwise  have  been  fatal. 

During  the  past  two  or  three  years  numerous  additional 
experiments  have  been  reported  which  confirm  the  results 
already  referred  to,  and  show  that  immunity  may  be  produced 
in  a  similar  manner  against  the  toxic  products  of  various  other 
pathogenic  bacteria,  —  the  typhoid  bacillus,  the  "  colon  "  bacillus, 
streptococcus  pyogenes,  staphylococcus  pyogenes  aureus  and 
albus,  etc. 

The  Italian  investigators,  Tizzoni  and  Centanni,  in  1892, 
published  a  preliminary  communication  in  which  they  gave  the 
results  of  experiments  which  appear  to  show  that  in  guinea 
pigs  treated  with  tuberculin,  by  Koch's  method,  a  substance 
is  developed  which  neutralizes  the  pathogenic  potency  of 
the  tubercle  bacillus.  Professor  Tizzoni  and  his  associate, 
Dr.  Schwarz,  have  also  (1892)  obtained  evidence  that  there  is 
an  antitoxin  of  rabies.  Blood-serum  taken  from  a  rabbit 
having  an  artificial  immunity  against  this  disease  was  found  to 
neutralize  in  vitro  the  virulence  of  the  spinal  marrow  of  a  rabid 
animal  after  a  contact  of  five  hours.  The  blood-serum  of  dogs 
having  an  acquired  immunity  against  rabies  was  found  to  have 
a  similar  action,  but  in  much  less  degree.  The  substance 
(antitoxin)  present  in  the  blood-serum  of  an  immune  rabbit 


IMMUNITY.  25 

does  not  dialyze ;  it  is  precipitated  by  alcohol,  and  preserves 
its  activity,  to  a  considerable  extent,  after  precipitation.  It  is 
soluble  in  glycerin,  and  is  said  to  have  the  general  characters 
of  a  "globulin."  The  experimenters  named  also  succeeded  in 
conferring  immunity  upon  susceptible  animals  by  injecting  into 
them  blood-serum  containing  this  antitoxin.  According  to  the 
Italian  investigators  named,  the  antitoxins  of  tetanus  and  of 
rabies  are  found  only  in  the  blood-serum  of  immune  animals, 
and  not  in  the  tissues  (nervous  or  muscular),  or  in  the  paren- 
chyma of  the  various  organs. 

Professor  Ehrlich,  of  Berlin,  in  1891,  published  the  results  of 
some  researches  which  have  an  important  bearing  upon  the 
explanation  of  acquired  immunity,  and  which  show  that  suscepti- 
ble animals  may  be  made  immune  against  the  action  of  certain 
toxic  proteids  of  vegetable  origin,  other  than  those  produced 
by  bacteria  ;  also  that  this  immunity  depends  upon  the  pres- 
ence of  an  antitoxin  in  the  blood-serum  of  the  immune  animals. 

In  a  later  paper  (1892)  Ehrlich  has  given  an  account  of 
subsequent  experiments  which  show  that  the  young  of  mice, 
which  have  an  acquired  immunity  for  these  vegetable  toxal- 
bumins,  may  acquire  immunity  from  the  ingestion  of  their 
mother's  milk  ;  and  also  that  immunity  from  tetanus  may  be 
acquired  in  a  brief  time  by  young  mice  through  their  mother's 
milk.  In  his  tetanus  experiments  Ehrlich  used  blood-serum 
from  an  immune  horse  to  give  immunity  to  the  mother-mouse 
when  her  young  were  already  seventeen  days  old.  Of  this 
blood-serum  2  c.c.  was  injected  at  a  time  on  two  successive 
days.  The  day  after  the  injection  one  of  the  sucklings  received 
a  tetanus  inoculation,  by  means  of  a  splinter  of  wood  to  which 
spores  were  attached.  The  animal  remained  in  good  health, 
while  a  much  larger  control  mouse,  inoculated  in  the  same  way, 
died  of  tetanus  at  the  end  of  twenty-six  hours.  Other  suck- 
lings, inoculated  at  the  end  of  forty-eight  hours  and  of  seventy- 
two  hours  after  the  mother  had  received  the  injection  of  blood- 
serum,  likewise  remained  in  good  health,  while  the  control 
mice  died. 

The  possibility  of  conferring  immunity  by  means  of  the  milk 
of  an  immune  animal  is  further  shown  by  the  experiments  of 


26  BIOLOGICAL   LECTURES. 

Brieger  and  Ehrlich  (1892).  A  female  goat  was  immunized 
against  tetanus  by  the  daily  injection  of  "thymus  tetanus 
bouillon."  The  dose  was  gradually  increased  from  0.2  c.c.  to 
10  c.c.  At  the  end  of  thirty-seven  days  a  mouse,  which 
received  o.i  c.c.  of  the  milk  of  this  goat  in  the  cavity  of  the 
abdomen,  proved  to  be  immune  against  tetanus.  Further 
experiments  gave  a  similar  result,  even  when  the  milk  of  the 
goat  was  not  injected  into  the  peritoneal  cavity  of  the  mouse 
until  several  hours  after  inoculation  with  a  virulent  culture  of 
the  tetanus  bacillus. 

In  a  subsequent  communication  (1893)  Brieger  and  Ehrlich 
describe  their  method  of  obtaining  the  antitoxin  of  tetanus 
from  milk  in  a  more  concentrated  form.  They  found  by  experi- 
ment that  it  was  precipitated  by  ammonium  sulphate  and  mag- 
nesium sulphate.  From  twenty-seven  to  thirty  per  cent  of 
ammonium  sulphate  added  to  milk  caused  a  precipitation  of 
the  greater  part  of  the  antitoxin.  This  precipitate  was  dis- 
solved in  water,  dialyzed  in  running  water,  then  filtered  and 
evaporated  in  shallow  dishes  at  35°  C.  in  a  vacuum.  One  liter 
of  milk  from  an  immune  goat  gave  about  i  gm.  of  a  trans- 
parent, yellowish-white  precipitate,  which  contained  fourteen 
per  cent  of  ammonium  sulphate.  This  precipitate  had  from 
four  hundred  to  six  hundred  times  the  potency  of  the  milk 
from  which  it  was  obtained  in  neutralizing  the  tetanus  toxin. 

A  most  interesting  question  presents  itself  in  connection 
with  the  discovery  of  the  antitoxins.  Does  the  animal  which 
is  immune  from  the  toxic  action  of  any  particular  toxalbumin 
also  have  an  immunity  for  other  toxic  proteids  of  the  same 
class }  The  experimental  evidence  on  record  indicates  that  it 
does  not.  In  Ehrlich's  experiments  with  ricin  and  abrin  he 
ascertained  that  an  animal  which  had  been  made  immune 
against  one  of  these  substances  was  quite  as  susceptible  to  the 
toxic  action  of  the  other  as  if  it  did  not  possess  this  immunity,  — 
i.e.  the  antitoxin  of  ricin  does  not  destroy  abrin,  and  vice  versa. 
As  an  illustration  of  the  fact  he  states  that  in  one  experiment 
a  rabbit  was  made  immune  for  ricin  to  such  an  extent  that  the 
introduction  into  its  eye  of  this  substance  in  powder  produced 
no  inflammatory  reaction  ;  but  the  subsequent  introduction  of 


IMMUNITY.  2  7 

a  solution  of  abrin,  of  i  to  10,000,  caused  a  violent  inflam- 
mation. In  this  connection  we  may  remark  that  there  is 
some  evidence  to  show  that  persons  who  are  repeatedly  stung 
by  certain  poisonous  insects  —  mosquitoes,  bees  —  acquire  a 
greater  or  less  degree  of  immunity  from  the  distressing  local 
effects  of  their  stings. 

We  have  also  experimental  evidence  that  animals  may 
acquire  a  certain  degree  of  immunity  from  the  toxic  action  of 
the  venom  of  the  rattlesnake.  This  was  first  demonstrated  by 
Sewall  {1887),  and  has  been  recently  confirmed  by  Calmette 

(1894). 

The  experimental  evidence  recorded  justifies  the  conclusion 
that  in  the  diseases  referred  to  acquired  immunity  depends, 
chiefly  at  least,  upon  the  presence  of  a  peculiar  proteid  sub- 
stance in  the  blood  of  the  immune  animal  —  antitoxin  — 
which  neutralizes  the  toxic  substance  —  toxin  or  toxalbumin 
—  to  which  the  morbid  phenomena  which  characterize  the 
disease  are  due. 

But  it  would  be  premature  to  infer  that  in  all  infectious 
diseases  immunity  depends  upon  the  production  of  an  antitoxin 
in  the  blood  of  the  immune  animal.  Indeed,  we  have  experi- 
mental evidence  which  shows  that  in  certain  cases  the  blood- 
serum  of  immune  animals  has  no  antitoxic  power,  but  acts 
upon  the  germ  itself,  instead  of  upon  its  toxic  products. 

It  may  be  worth  while  to  refer  briefly,  before  closing,  to 
some  examples  of  acquired  immunity  of  a  different  order.  We 
refer  to  the  tolerance  of  extremes  of  heat  and  cold  which  may 
be  established  by  habitual  exposure,  and  more  especially  to  the 
tolerance  to  narcotics  and  irritant  poisons,  which  is  very 
remarkable,  and  has  never  been  explained  in  a  satisfactory 
manner.  A  recent  writer  (Samuel,  1892)  has  presented  experi- 
mental evidence  which  shows  that  the  local  inflammation  which 
results  from  the  application  of  croton  oil  to  the  ear  of  a  rab- 
bit does  not  occur  when  a  second  application  is  made  to  the 
same  ear  after  recovery  from  the  effects  of  the  first.  That  a 
tolerance  may  be  acquired  to  comparatively  large  doses  of 
arsenic  is  well  known,  and  the  tolerance  which  the  victims  of 
drug  habits  acquire  to  enormous  doses  of  narcotics  is  a  matter 


28  BIOLOGICAL   LECTURES. 

of  daily  observation.  In  the  writer's  paper  on  acquired  immu- 
nity, published  in  i88r,  an  attempt  is  made  to  account  for 
acquired  immunity  in  infectious  diseases  as  analogous  to  the 
immunity  to  drugs  just  referred  to.  But  it  is  evident  that  in 
the  present  state  of  science  the  analogy  is  incomplete,  and 
possibly  delusive,  in  the  absence  of  any  experimental  evidence 
of  the  presence  of  specific  antitoxins  in  the  blood  of  those  who, 
as  a  result  of  habit,  tolerate  excessive  doses  of  morphia,  cocaine, 
narcotin,  etc. 


THIRD    LECTURE. 


A    STUDENT'S   REMINISCENCES    OF    HUXLEY. 

HENRY    FAIRFIELD    OSBORN. 

(Columbia  College,   N.  Y.) 

By  far  the  larger  number  of  American  students  who  go 
abroad  pass  through  the  English  Channel,  obtain  a  distant 
view  of  the  mother  country,  and  after  from  one  to  three  years 
in  Germany,  return  with  an  exclusively  German  education. 
Having  visited  neither  England  nor  France,  the  implication 
is  that  the  countries  which  produced  Owen,  Darwin,  Huxley, 
Balfour,  or  Lamarck,  Cuvier,  St.  Hilaire,  and  Pasteur  have 
nothing  to  offer  the  American  student.  But  this  is  not  the 
fact.  The  fact  is  that  England  and  France  are  a  half-century 
behind  Germany  in  that  kind  of  university  organization  which 
attracts  a  foreign  student,  and  enables  him  immediately  to  find 
his  level  and  enter  upon  his  research.  English  and  French 
universities  until  a  very  recent  date  have  been  either  not  so 
fully  prepared,  or  have  met  the  newcomer  with  practically 
insuperable  obstacles  in  the  matter  of  a  degree. 

None  the  less,  the  student  who  has  not  breasted  these 
obstacles  for  the  compensating  advantages  which  the  English 
and  French  schools  offer  has  made  a  serious  mistake.  He  has 
brought  back  not  an  Old  World  education,  but  an  exclusively 
German  education,  with  its  splendidly  sound  and  unique 
features,  and  with  many  inherent  defects.  Germany  produces 
the  generals  and  the  rank  and  file  of  the  armies  of  science, 
but  certainly  the  commanders-in-chief,  in  biology  at  least,  have 
been  Englishmen.  If  we  find  the  highest  exponents  of  purely 
inductive  research  in  Germany,  we  certainly  find  a  better  union 


30  BIOLOGICAL  LECTURES. 

of  the  inductive  and  deductive  methods  in  France  and  England. 
France  leads  in  expression  and  style  of  thought,  although,  upon 
the  whole,  less  sound  in  substance  than  Germany.  England, 
and  France  in  her  best  period,  have  given  us  the  most  far- 
reaching  and  permanent  generalizations  in  biology.  It  follows 
that  the  American  student  who  can  afford  the  experience  will 
profit  most  by  placing  himself  successively  in  the  scientific 
atmosphere  of  Germany,  France,  and  England.  My  own  post- 
graduate education  was  unfortunately  not  of  this  three-sided 
type.  None  the  less,  it  has  always  seemed  a  most  fortunate 
circumstance  that  in  the  spring  of  1879  a  letter  from  the  vener- 
able Kitchen  Parker  led  me  to  Cambridge,  and  to  the  great 
privilege  of  sitting  under  Balfour,  the  most  brilliant  and  lovable 
of  men.  In  the  following  autumn  Huxley's  lectures  upon 
Comparative  Zoology  began  in  October,  and  by  entering  this 
course  I  came  to  know  personally  this  great  master,  and 
through  him  enjoyed  the  rare  opportunity  of  meeting  Charles 
Darwin.  After  this  experience,  which  was  equally  open  to  any 
serious  student  of  biology  at  that  time,  it  is  natural  that  I 
should  strongly  advise  those  of  you  who  are  planning  your 
foreign  studies  to  spend  part  of  your  time  in  England,  and 
endeavor  to  discern  some  of  the  distinctive  qualities  of  English 
men  of  science  which  Huxley  so  nobly  illustrated.  You  will 
pardon  the  personal  element  in  the  following  recollections  of 
Huxley  as  a  teacher,  and  the  rather  informal  review  of  his  life 
work. 

Huxley,  as  a  teacher,  can  never  be  forgotten  by  any  of  his 
students.  He  entered  his  lecture-room  promptly  as  the  clock 
was  striking  nine,  rather  quickly,  and  with  his  head  bent  forward 
*'  as  if  oppressive  with  its  mind."  He  usually  glanced  attention 
to  his  class  of  about  ninety,  and  began  speaking  before  he 
reached  his  chair.  He  spoke  between  his  lips,  but  with  per- 
fectly clear  analysis,  with  thorough  interest,  and  with  philo- 
sophic insight  which  was  far  above  the  average  of  his  students. 
He  used  very  few  charts,  but  handled  the  chalk  with  great 
skill,  sketching  out  the  anatomy  of  an  animal  as  if  it  were  a 
transparent  object.  As  in  Darwin's  face,  and  as  in  Erasmus 
Darwin's  or  Buffon's,  and  many  other  anatomists  with  a  strong 


A    STUDENT'S  REMINISCENCES   OF  HUXLEY, 


31 


sense  of  form,  his  eyes  were  heavily  overhung  by  a  projecting 
forehead  and  eyebrows,  and  seemed  at  times  to  look  inward. 
His  lips  were  firm  and  closely  set,  with  the  expression  of  posi- 
tiveness,  and  the  other  feature  which  most  marked  him  was 
the  very  heavy  mass  of  hair  falling  over  his  forehead,  which  he 
would  frequently  stroke  or  toss  back.  Occasionally  he  would 
lighten  up  the  monotony  of  anatomical  description  by  a  bit  of 
humor.  I  remember  one  instance  which  was  probably  reminis- 
cent of  his  famous  tilt  with  Bishop  Wilberforce  at  the  meeting 
of  the  British  Association  in  i860.  Huxley  was  describing 
the  mammalian  heart,  and  had  just  distinguished  between  the 
tricuspid  valve  on  the  right  side  of  the  heart  and  the  bicuspid 
valve  on  the  left,  which  you  know  resembles  a  bishop's  miter, 
and  hence  is  known  as  the  mitral  valve.  He  said,  "  It  is  not 
easy  to  recall  on  which  side  these  respective  valves  are  found, 
but  I  recommend  this  rule  :  you  can  easily  remember  that  the 
mitral  is  on  the  left,  because  a  bishop  is  never  known  to  be  on 
the  right." 

Huxley  was  the  father  of  modern  laboratory  instruction ;  but 
in  1879  h^  "^^s  so  intensely  engrossed  with  his  own  researches 
that  he  very  seldom  came  through  the  laboratory,  which  was 
ably  directed  by  T.  Jeffrey  Parker,  assisted  by  Howes  and 
W.  Newton  Parker,  all  of  whom  are  now  professors,  Howes 
having  succeeded  to  Huxley's  chair.  Each  visit,  therefore, 
inspired  a  certain  amount  of  terror,  which  was  really  unwar- 
ranted, for  Huxley  always  spoke  in  the  kindest  tones  to  his 
students,  although  sometimes  he  could  not  resist  making  fun 
at  their  expense.  There  was  an  Irish  student  who  sat  in  front 
of  me,  whose  anatomical  drawings  in  water  color  were  certainly 
most  remarkable  productions.  Huxley,  in  turning  over  his 
drawing-book,  paused  at  a  large  blur,  under  which  was  carefully 
inscribed,  "sheeps'  liver,"  and  smilingly  said,  "I  am  glad  to 
know  that  is  a  liver ;  it  reminds  me  as  much  of  Cologne 
cathedral  in  a  fog  as  of  anything  I  have  ever  seen  before." 
Fortunately  the  nationality  of  the  student  enabled  him  to  fully 
appreciate  the  humor. 

The  greatest  event  in  the  winter  of  1879  was  Darwin's  first 
and   only   visit    to  the  laboratory.     They  came  in   together. 


32  BIOLOGICAL   LECTURES. 

Huxley  leading  slowly  down  the  long  narrow  room,  pointing 
out  the  especial  methods  of  teaching  which  he  had  originated 
and  which  are  now  universally  adopted  in  England  and  in  this 
country.  Darwin  was  instantly  recognized  by  the  class  as  he 
entered,  and  a  thrill  of  curiosity  passed  down  the  room,  for  no 
one  present  had  ever  even  seen  him  before.  I  remember  my  own 
feelings  very  distinctly.  I  was  just  finishing  a  laborious  dissec- 
tion of  the  lobster's  nervous  system,  and  out  of  politeness  and 
deference  to  laboratory  discipline,  pretended  to  continue  my 
work,  with  results  fatal  to  the  nervous  system  of  the  crustacean. 
As  the  pair  came  back  up  the  room  Huxley  singled  me  out,  I 
suppose  because  I  was  the  only  foreign  student,  and  introduced 
me  to  Darwin,  —  the  greatest  kindness  he  could  have  shown  a 
young  student.  There  was  the  widest  possible  contrast  in  the 
two  faces.  Darwin's  grayish- white  hair  and  bushy  eyebrows 
overshadowed  the  pair  of  deeply  set  blue  eyes,  which  seemed 
to  image  his  wonderfully  calm  and  deep  vision  of  nature,  and 
at  the  same  time  to  emit  benevolence.  Huxley's  piercing 
black  eyes  and  determined  and  resolute  face  were  full  of 
admiration  and  at  the  same  time  protection  of  his  older  friend. 
He  said  afterwards :  "  You  know  I  have  to  take  care  of  him  — 
in  fact,  I  have  always  been  Darwin's  bull-dog,"  and  this  exactly 
expressed  one  of  the  many  relations  which  existed  so  long 
between  the  two  men. 

Huxley  was  not  always  fortunate  in  the  intellectual  caliber 
of  the  men  to  whom  he  lectured  in  the  Royal  School  of  Mines. 
Many  of  the  younger  generation  were  studying  in  the  univer- 
sities, under  Balfour  at  Cambridge  and  under  Rolleston  at 
Oxford.  However,  Saville  Kent,  C.  Lloyd  Morgan,  George  B. 
Howes,  T.  Jeffrey  Parker,  and  W.  Newton  Parker  are  repre- 
sentative biologists  who  were  wholly  trained  by  Huxley.  Many 
others,  not  his  students,  have  expressed  the  deepest  indebted- 
ness to  him.  Among  these,  especially,  are  Prof.  E.  Ray 
Lankester,  of  Oxford,  and  Prof.  Michael  Foster,  of  Cambridge. 
Huxley  once  said  that  he  had  *' discovered  Foster."  He  not 
only  singled  men  out,  but  knew  how  to  direct  and  inspire  them 
to  investigate  the  most  pressing  problems  of  the  day.  As  it 
was,  his  thirty-one  years  of  lectures  would  have  produced  a  far 


A    STUDENT'S  REMINISCENCES   OF  HUXLEY.        33 

greater  effect  if  they  had  been  delivered  from  an  Oxford,  Cam- 
bridge, or  Edinburgh  chair.  In  fact,  Huxley's  whole  life  would 
have  been  different,  in  some  ways  more  effective,  in  others 
less  so,  if  the  universities  had  welcomed  the  young  genius 
who  was  looking  for  a  post,  and  even  cast  his  eyes  toward 
America  in  1850;  but  in  those  early  days  of  classical  prestige 
both  seats  of  learning  were  dead  to  the  science,  which  it  was 
Huxley's  great  service  in  support  of  Darwin  to  place  beside 
physics,  in  the  lead  of  all  others  in  England.  Moreover, 
Oxford,  if  not  Cambridge,  could  not  long  have  sheltered  such 
a  wolf  in  the  fold. 

Huxley's  public  addresses  always  gave  the  impression  of 
being  largely  impromptu ;  but  he  once  told  me :  "  I  always 
think  out  carefully  every  word  I  am  going  to  say.  There  is 
no  greater  danger  than  the  so-called  inspiration  of  the  moment^ 
which  leads  you  to  say  something  which  is  not  exactly  true,  or 
which  you  would  regret  afterward.  I  sometimes  envy  your 
countrymen  their  readiness,  and  believe  that  a  native  Ameri- 
can, if  summoned  out  of  bed  at  midnight,  could  step  to  his 
window  and  speak  well  upon  any  subject."  I  told  him  I  feared 
he  had  been  slightly  misinformed.  I  feared  that  many  Ameri- 
can impromptu  speeches  were  more  distinguished  by  a  flow  of 
language  than  of  ideas.  But  Huxley  was  sometimes  very 
impressive  when  he  did  not  speak.  In  1879  ^^  ^^^  strongly 
advocating  the  removal  of  the  Royal  School  of  Mines  from 
crowded  Jermyn  Street  to  South  Kensington,  —  a  matter  which 
is  still  being  agitated.  At  a  public  dinner  given  by  the  alumni 
of  the  school,  who  were  naturally  attached  to  the  old  buildings, 
the  chairman  was  indiscreet  enough  to  make  an  attack  upon 
the  policy  of  removal.  He  was  vigorously  applauded,  when,  to 
every  one's  consternation,  Huxley,  who  was  sitting  at  the 
chairman's  right,  slowly  rose,  paused  a  moment,  and  then 
silently  skirted  the  tables  and  walked  out  of  the  hall.  A 
solemn  pall  fell  over  the  remainder  of  the  dinner,  and  we  were 
all  glad  to  find  an  excuse  to  leave  early. 

In  personal  conversation  Huxley  was  full  of  humor  and 
greatly  enjoyed  stories  at  his  own  expense.  Such  was  the  fol- 
lowing :  **  In  my  early  period  as  a  lecturer,  I  had  very  little 


34  BIOLOGICAL   LECTURES. 

confidence  in  my  general  powers,  but  one  thing  I  prided  my- 
self upon  was  clearness.  I  was  once  talking  of  the  brain 
before  a  large,  mixed  audience,  and  soon  began  to  feel  that  no 
one  in  the  room  understood  me.  Finally  I  saw  the  thoroughly 
interested  face  of  a  woman  auditor,  and  took  consolation  in 
delivering  the  remainder  of  the  lecture  directly  to  her.  At 
the  close,  my  feeling  as  to  her  interest  was  confirmed  when 
she  came  up  and  asked  if  she  might  put  one  question  upon  a 
single  point  which  she  had  not  quite  understood.  *  Certainly,' 
I  replied.  '  Now  Professor,'  she  said,  *  is  the  cerebellum  inside 
or  outside  of  the  skull .?'  "  Once,  speaking  of  his  deafness,  he 
said  :  ''  It  is  a  great  misfortune  to  be  deaf  in  only  one  ear. 
Every  time  I  dine  out,  the  lady  sitting  by  my  good  ear  thinks 
I  am  charming,  but  I  make  a  mortal  enemy  of  the  lady  on  my 
deaf  side."  A  story  of  his  about  babies  is  also  characteristic  : 
''When  a  fond  mother  calls  upon  me  to  admire  her  baby  I 
never  fail  to  respond ;  and,  while  cooing  appropriately,  I  take 
advantage  of  an  opportunity  to  gently  ascertain  whether  the 
soles  of  its  feet  turn  in  and  tend  to  support  my  theory  of 
arboreal  descent." 

Huxley's  life  is  as  full  of  suggestion  to  the  student  as  were 
his  lectures  and  his  conversation.  It  illustrates  the  force  of 
obtaining  a  very  broad  view  of  the  animal  kingdom  before  we 
attempt  to  enter  the  plane  of  higher  generalization.  Huxley's 
training  in  embryology,  vertebrate  and  invertebrate  zoology, 
palaeontology,  and  geology  was  not  mapped  out  for  him  as 
for  the  modern  university  student.  His  prolonged  sea-voyage 
gave  him  time  and  material  for  reflection,  and  after  this  he 
was  led  from  one  subject  to  another  until  he  obtained  a  grasp 
of  nature  as  a  whole,  second  only  to  that  of  Darwin. 

Huxley  was  born  in  1825.  Like  Goethe,  he  inherited  from 
his  mother  his  brilliantly  alert  powers  of  thought,  and  from  his 
father,  his  courage  and  tenacity  of  purpose, —  a  combination  of 
qualities  which  especially  fitted  him  for  the  period  in  which  he 
was  to  live.  There  is  nothing  striking  recorded  about  his  boy- 
hood as  a  naturalist.  He  preferred  engineering,  but  was  led 
into  medicine. 

At  the  close  of  his  medical  course  he  secured  a  navy  medical 


A    STUDENT'S  REMINISCENCES   OF  HUXLEY.        35 

post  upon  the  "  Rattlesnake."  This  brought  with  it,  as  to 
Darwin,  the  training  of  a  four-years'  voyage  to  the  South  Seas 
off  eastern  Australia  and  west  Guinea  —  a  more  liberal  educa- 
tion to  a  naturalist  than  any  university  affords,  even  at  the 
present  day.  This  voyage  began  at  twenty-one,  and  he  says  of 
it :  "  But,  apart  from  experience  of  this  kind  and  the  oppor- 
tunity offered  for  scientific  work  to  me,  personally,  the  cruise 
was  extremely  valuable.  It  was  good  for  me  to  live  under 
sharp  discipline,  to  be  down  on  the  realities  of  existence  by 
living  on  bare  necessities,  to  find  out  how  extremely  worth 
living  life  seemed  to  be,  when  one  woke  from  a  night's  rest  on 
a  soft  plank,  with  the  sky  for  a  canopy,  and  cocoa  and  weevily 
biscuit  the  sole  prospect  for  breakfast,  and  more  especially  to 
learn  to  work  for  what  I  got  for  myself  out  of  it.  My  brother 
officers  were  as  good  as  sailors  ought  to  be  and  generally  are ; 
but,  naturally,  they  neither  knew  nor  cared  anything  about  my 
pursuits,  nor  understood  why  I  should  be  so  zealous  in  the 
pursuit  of  the  objects  which  my  friends,  the  middies,  christened 
'Buffons,'  after  the  title  conspicuous  on  a  volume  of  the  Suites 
a  Biiffon,  which  stood  in  a  prominent  place  on  my  shelf  in  the 
chart-room." 

As  a  result  of  this  voyage  of  four  years,  numerous  papers 
were  sent  home  to  the  Linnaean  Society,  of  London,  but  few 
were  published.  Upon  his  return,  his  first  work.  Upon  the 
Anatomy  and  Affinities  of  the  Medusce^  was  declined  for  publica- 
tion by  the  Admiralty  —  a  fortunate  circumstance,  for  it  led  to 
his  quitting  the  navy  for  good  and  trusting  to  his  own  re- 
sources. Upon  publication  (1849)  this  memoir  at  once  estab- 
lished his  scientific  reputation  at  the  early  age  of  twenty-four, 
just  as  Richard  Owen  had  won  his  spurs  by  his  Memoir  on 
the  Pearly  Nautilus.  In  1852  Huxley's  preference  as  a  biolo- 
gist was  to  turn  back  to  physiology,  which  had  become  his 
favorite  study  in  the  medical  course.  But  his  fate  was  to  enter 
and  become  distinguished  in  a  widely  different  branch,  which  had 
as  little  attraction  for  him  as  for  most  students  of  marine  life, 
namely,  palaeontology.     He  says  of  this  sudden  change  of  base  : 

'*At  last,  in  1854,  on  the  translation  of  my  warm  friend 
Edward   Forbes  to   Edinburgh,   Sir   Henry  de  la  Beche,  the 


36  BIOLOGICAL   LECTURES. 

Director-General  of  the  Geological  Survey,  offered  me  the  post 
Forbes  had  vacated  of  Palaeontologist  and  Lecturer  on  Natural 
History.  I  refused  the  former  point-blank,  and  accepted  the 
latter  only  provisionally,  telling  Sir  Henry  that  I  did  not  care 
for  fossils,  and  that  I  should  give  up  natural  history  as  soon  as 
I  could  get  a  physiological  post.  But  I  held  the  office  for 
thirty-one  years,  and  a  large  part  of  my  work  has  been  palae- 
ontological." 

From  this  time  until  1885  his  labors  extended  over  the 
widest  field  of  biology  and  of  philosophy  ever  covered  by  any 
naturalist,  with  the  single  exception  of  Aristotle.  In  philos- 
ophy Huxley  showed  rare  critical  and  historical  power.  He 
made  the  most  exhaustive  study  of  Hume,  but  his  own  philo- 
sophical spirit  and  temper  was  more  directly  the  offspring  of 
Descartes.  Some  subjects  he  mastered,  others  he  merely 
touched ;  but  every  subject  which  he  wrote  about  he  illumi- 
nated. Huxley  did  not  discover  or  first  define  protoplasm,  but 
he  made  it  known  to  the  English-speaking  world  as  the  physical 
basis  of  life  —  recognizing  the  unity  of  animal  and  plant  proto- 
plasm. He  cleared  up  certain  problems  among  the  Protozoa. 
In  1849  appeared  his  great  work  upon  the  oceanic  Hydrozoa^ 
and  familiarity  with  these  forms  doubtless  suggested  the  bril- 
liant comparison  of  the  two-layered  gastrula  to  the  adult 
hydrozoa.  He  threw  light  upon  the  Tunicata,  describing  the 
endostyle  as  a  universal  feature,  but  not  venturing  to  raise  the 
Tunicata  to  a  separate  order.  He  set  in  order  the  cephalopod 
mollusca,  deriving  the  spiral  from  the  straight-shelled  fossil 
forms.  He  contributed  to  the  Arthropoda,  his  last  word  upon 
this  group  being  his  charming  little  volume  upon  the  Cray- 
fish,—  a  model  of  its  kind.  But  think  of  the  virgin  field  which 
opened  up  before  him  among  the  vertebrata,  when  in  1859  he 
was  the  first  to  perceive  the  truth  of  Darwin's  theory  of  descent. 
Here  were  Cuvier's  and  Owen's  vast  researches  upon  living  and 
extinct  forms,  a  disorderly  chaos  of  facts  waiting  for  generali- 
zation. Huxley  was  the  man  for  the  time.  He  had  already 
secured  a  thoroughly  philosophical  basis  for  his  comparative 
osteology  by  studying  the  new  embryology  of  Von  Baer,  which 
Richard    Owen    had    wholly   ignored.       In    1858    his    famous 


A    STUDENT'S  REMINISCENCES   OF  HUXLEY.        37 

Croonian  lecture  on  the  "•  Theory  of  the  Vertebrate  Skull " 
gave  the  deathblow  to  Owen's  life-work  upon  the  skull  and 
vertebral  archetype,  and  to  the  whole  system  of  mystical  and 
transcendental  anatomy  ;  and  now  Huxley  set  to  work  vigor- 
ously to  build  out  of  Owen's  scattered  tribes  the  great  limbs 
and  branches  of  the  vertebrate  tree.  He  set  the  fishes  and 
batrachia  apart  as  the  Icthyopsidan  branch,  the  reptiles  and 
birds  as  the  Satcropsidan  in  contrast  with  the  Mammalian^ 
which  he  derived  from  a  pro-sauropsidan  or  amphibian  stem, — 
,a  theory  which,  with  some  modification,  has  received  strong 
recent  verification. 

Professor  Owen,  who  had  held  undisputed  sway  in  England 
up  to  1858,  fought  nobly  for  opinions  which  had  been  idolized 
in  the  first  half-century,  but  was  routed  at  every  point.  Hux- 
ley captured  his  last  fortress  when,  in  his  famous  essay  of 
1865,  "Man's  Place  in  Nature,"  he  undermined  Owen's  teach- 
ing of  the  separate  and  distinct  anatomical  position  of  man. 
We  can  only  appreciate  Huxley's  fighting-qualities  when  we 
see  how  strongly  Owen  was  intrenched  at  the  beginning  of 
this  long  battle  royal.  He  was  director  of  the  British  Museum, 
and  occupied  other  high  posts  ;  he  had  the  strong  moral  sup- 
port of  the  government  and  of  the  royal  family,  although  these 
were  weak  allies  in  a  scientific  encounter. 

Huxley's  powers  of  rapid  generalization  of  course  betrayed 
him  frequently.  His  Bathybius  was  a  groundless  and  short- 
lived hypothesis  ;  he  went  far  astray  upon  the  phylogeny  of 
the  horses.  But  these  and  other  errors  were  far  less  attribu- 
table to  defects  in  his  reasoning  powers  than  to  the  extraordi- 
narily high  pressure  under  which  he  worked  for  the  twenty 
years  between  i860  and  1880,  when  duties  upon  the  Educa- 
tional Board,  upon  the  Government  Fisheries  Commission, 
and  upon  Parliamentary  committees  crowded  upon  him.  He 
had  at  his  command  none  of  the  resources  of  modern  tech- 
nique. He  cut  his  own  sections.  I  remember  once  seeing 
some  of  his  microscopic  sections.  To  one  of  our  college 
junior  students  working  with  a  Minot  microtome  Huxley's 
sections  would  have  appeared  like  a  translucent  beefsteak, 
—  another    illustration    that    it    is    not    always    the    section 


38  BIOLOGICAL   LECTURES. 

which  reveals  the  natural  law,  but  the  man  who  looks  at  the 
section. 

Huxley  was  not  only  a  master  in  the  search  for  truth,  but  in 
the  way  in  which  he  presented  it,  both  in  writing  and  in  speak- 
ing ;  and  we  are  assured,  largely  as  he  was  gifted  by  nature, 
his  beautifully  lucid  and  interesting  style  was  partly  the  result 
of  deliberate  hard  work.  He  was  not  born  to  it ;  some  of  his 
early  essays  are  very  labored.  He  acquired  it.  He  was  familiar 
with  the  best  Greek  literature,  and  restudied  the  language.  He 
pored  over  Milton  and  Carlyle  and  Mill.  He  studied  the  fine 
old  English  of  the  Bible.  He  took  as  especial  models  Hume 
and  Hobbes,  until  finally  he  wrote  his  mother  tongue  as  no 
other  Englishman  wrote  it.  Take  up  any  one  of  his  essays,  — 
biological,  literary,  philosophical;  you  at  once  see  his  central  idea 
and  his  main  purpose,  although  he  never  uses  italics  or  spaced 
letters  as  many  of  our  German  masters  do  to  relieve  the 
obscurity  of  their  sentences.  We  are  carried  along  upon  the 
broad  current  of  his  reasoning  without  being  confused  by  his 
abundant  side  illustrations.  He  gleaned  from  the  literature  of 
all  time  until  his  mind  was  stocked  with  apt  similes.  Who  but 
Huxley  would  have  selected  the  title  "  Lay  Sermons  "  for  his 
first  volume  of  addresses;  or,  in  1880,  twenty-one  years  after 
Darwin's  work  appeared,  would  have  entitled  his  essay  upon 
the  influence  of  this  work,  "■  The  Coming  of  Age  of  the  Origin 
of  Species"  .?  Or  to  whom  else  would  it  have  occurred  to  repeat 
over  the  grave  of  Balfour  the  exquisitely  appropriate  lines  :  — 

"  For  Lycidas  is  dead,  dead  ere  his  prime, 
Young  Lycidas,  and  hath  not  left  his  peer." 

Who  else  could  have  inveighed  thus  against  modern  specializa- 
tion :  "  We  are  in  the  case  of  Tarpeia,  who  opened  the  gates  of 
the  Roman  citadel  to  the  Sabines  and  was  crushed  by  the  weight 
of  the  reward  bestowed  upon  her.  It  has  become  impossible 
for  any  man  to  keep  pace  with  the  progress  of  the  whole  of 
any  important  branch  of  science.  It  looks  as  if  the  scientific, 
like  other  revolutions,  meant  to  devour  its  own  children  ;  as  if 
the  growth  of  science  tended  to  overwhelm  its  votaries ;  as 
if  the  man  of  science  of  the  future  were  condemned  to  diminish 


A    ST  (/DENT'S  REMINISCENCES    OF  HUXLEY.        39 

into  a  narrower  specialist  as  time  goes  on.  It  appears  to  me 
that  the  only  defence  against  this  tendency  to  the  degeneration 
of  scientific  workers  lies  in  the  organization  and  extension  of 
scientific  education  in  such  a  manner  as  to  secure  breadth  of 
culture  without  superficiality." 

What  Haeckel  did  for  evolution  m  Germany,  Huxley  did  in 
England.  As  the  earliest  and  most  ardent  supporter  of  Darwin 
and  the  theory  of  descent,  it  is  remarkable  that  he  never  gave 
an  unreserved  support  to  the  theory  of  natural  selection  as  all- 
sufficient.  Twenty-five  years  ago,  with  his  usual  penetration 
and  prophetic  insight,  he  showed  that  the  problem  of  variation 
might,  after  all,  be  the  greater  problem ;  and  only  three  years 
ago,  in  his  "  Romanes  Lecture,"  he  disappointed  many  of  the 
disciples  of  Darwin  by  declaring  that  natural  selection  failed  to 
explain  the  origin  of  our  moral  and  ethical  nature.  Whether 
he  was  right  or  wrong  we  will  not  stop  to  discuss,  but  consider 
the  still  more  remarkable  conditions  of  Huxley's  relations  to 
the  theory  of  evolution.  As  expositor,  teacher,  defender,  he 
was  the  high  priest  of  evolution.  From  the  first,  he  saw  the 
strong  and  weak  points  of  the  special  Darwinian  theory.  He 
wrote  upon  the  subject  for  thirty  years,  and  yet  he  never  con- 
tributed a  single  original  or  novel  idea  to  it ;  in  other  words, 
Huxley  added  vastly  to  the  demonstration,  but  never  added  to 
the  sum  of  either  theory  or  working  hypothesis,  and  the  con- 
temporary history  of  the  theory  proper  could  be  written  with- 
out mentioning  his  name.  This  lack  of  speculation  upon  the 
factors  of  evolution  was  true  throughout  his  whole  life.  In  the 
voyage  of  the  "  Rattlesnake  "  he  says  he  did  not  even  think  of 
the  species  problem.  His  last  utterance  regarding  the  causes  of 
evolution  appeared  in  one  of  the  Reviews  as  a  passing  criticism 
of  Weismann's  finished  philosophy,  in  which  he  implies  that  his 
own  philosophy  of  the  causes  of  evolution  was  as  far  off  as 
ever ;  in  other  words,  Huxley  never  fully  made  up  his  mind  or 
committed  himself  to  any  causal  theory  of  development. 

Taking  the  nineteenth  century  at  large,  outside  of  our  own 
circles  of  biology,  Huxley's  greatest  and  most  permanent 
achievement  was  his  victory  for  free  thought.  Personally  we 
may  not  be  agnostic  ;  we  may  disagree  with  much  that  he  has 


40  BIOLOGICAL   LECTURES. 

said  and  written,  but  we  must  admire  Huxley's  valiant  services 
none  the  less.  A  reformer  must  be  an  extremist,  and  Huxley 
was  often  extreme,  but  he  never  said  what  he  did  not  believe  to 
be  true.  If  it  is  easy  for  you  and  for  me  to  say  what  we  think 
in  print  and  out  of  print  now,  it  is  because  of  the  battles  fought 
by  such  men  as  Huxley  and  Haeckel.  When  Huxley  began  his 
great  crusade,  the  air  was  full  of  religious  intolerants  and,  what 
is  quite  as  bad,  scientific  shams.  If  Huxley  had  entered  the 
contest  carefully  and  guardedly,  he  would  have  been  lost  in  the 
enemy's  ranks  ;  but  he  struck  right  and  left  with  sledge-hammer 
blows,  whether  it  was  a  high  dignity  of  the  Church  or  of  the 
State.  Just  before  the  occasion  of  one  of  his  greatest  contests, 
that  with  Gladstone  in  the  pages  of  the  Contemporary  Review, 
Huxley  was  in  Switzerland  completely  broken  down  in  health, 
and  suffering  from  torpidity  of  the  liver.  Gladstone  had  written 
one  of  his  characteristically  brilliant  articles  upon  the  close  cor- 
respondence between  the  Order  of  Creation  as  revealed  in  the 
first  chapter  of  Genesis  and  the  Order  of  Evolution  as  shown 
by  modern  biology.  "When  this  article  reached  me,"  Huxley 
told  me,  "  I  read  it  through,  and  it  made  me  so  angry  that  I 
believe  it  must  have  acted  upon  my  liver.  At  all  events,  when 
I  finished  my  reply  to  Gladstone  I  felt  better  than  I  had  for 
months  past." 

Huxley's  last  public  appearance  was  at  the  meeting  of  the 
British  Association  at  Oxford.  He  had  been  very  urgently 
invited  to  attend,  for  exactly  a  quarter  of  a  century  before  the 
Association  had  met  at  Oxford,  and  Huxley  had  had  his  famous 
encounter  with  Bishop  Wilberforce.  It  was  felt  that  the  anni- 
versary would  be  an  historic  one,  and  incomplete  without  his 
presence,  and  so  it  proved  to  be.  Huxley's  especial  duty  was 
to  second  the  vote  of  thanks  for  the  Marquis  of  Salisbury's 
address, — one  of  the  invariable  formalities  of  the  opening 
meeting  of  the  Association.  The  meeting  proved  to  be  the 
greatest  one  in  the  history  of  the  Association.  The  Sheldonian 
theatre  was  packed  with  one  of  the  most  distinguished  scientific 
audiences  ever  brought  together,  and  the  address  of  the  Marquis 
was  worthy  of  the  occasion.  The  whole  tenor  of  it  was  the 
unknown  in  science.     Passing  from  the  unsolved  problems  of 


A    STUDENT'S  REMINISCENCES   OF  HUXLEY.        41 

astronomy,  chemistry,  and  physics,  he  came  to  biology.  With 
delicate  irony  he  spoke  of  the  "  comforting  word,  evolution,"  and 
passing  to  the  Weismannian  controversy,  implied  that  the  dia- 
metrically opposed  views  so  frequently  expressed  nowadays 
threw  the  whole  process  of  evolution  into  doubt.  It  was  only 
too  evident  that  the  Marquis  himself  found  no  comfort  in 
evolution,  and  even  entertained  a  suspicion. as  to  its  proba- 
bility. It  was  well  worth  the  whole  journey  to  Oxford  to 
watch  Huxley  during  this  portion  of  the  address.  In  his  red 
doctor-of-laws  gown,  placed  upon  his  shoulders  by  the  very 
body  of  men  who  had  once  referred  to  him  as  "a  Mr.  Huxley," 
he  sank  deeper  into  his  chair  upon  the  very  front  of  the  plat- 
form and  restlessly  tapped  his  foot.  His  situation  was  an 
unenviable  one.  He  had  to  thank  an  ex-Prime  Minister  of 
England,  and  present  Lord-Chancellor  of  Oxford  University, 
for  an  address  the  sentiments  of  which  were  directly  against 
those  he  himself  had  been  maintaining  for  twenty-five  years. 
He  said  afterward  that  when  the  proofs  of  the  Marquis' 
address  were  put  into  his  hands  the  day  before,  he  realized  that 
he  had  before  him  a  most  delicate  and  difficult  task.  Lord 
Kelvin  (Sir  William  Thompson),  one  of  the  most  distinguished 
living  physicists,  first  moved  the  vote  of  thanks  ;  but  his  recep- 
tion was  nothing  to  the  tremendous  applause  which  greeted 
Huxley  in  the  heart  of  that  university  whose  cardinal  princi- 
ples he  had  so  long  been  opposing.  Considerable  anxiety  had 
been  felt  by  his  friends  lest  his  voice  would  fail  to  fill  the 
theatre,  for  it  had  signally  failed  during  his  Romanes  Lecture 
delivered  in  Oxford  the  year  before  ;  but  when  Huxley  arose  he 
reminded  you  of  a  venerable  gladiator  returning  to  the  arena 
after  years  of  absence.  He  raised  his  figure  and  his  voice  to 
its  full  height,  and  with  one  foot  turned  over  the  edge  of  the 
step,  veiled  an  unmistakable  and  vigorous  protest  in  the  most 
gracious  and  dignified  speech  of  thanks. 

Throughout  the  subsequent  special  sessions  of  this  meeting 
Huxley  could  not  appear.  He  gave  the  impression  of  being 
aged  but  not  infirm,  and  no  one  realized  that  he  had  spoken 
his  last  word  as  champion  of  the  law  of  Evolution.  He  soon 
returned  to  Eastbourne.     Early  in   the  winter  he  contracted 


42  BIOLOGICAL   LECTURES. 

the  grippe,  which  passed  into  pneumonia.  He  rallied  once  or 
twice,  and  his  last  effort  to  complete  a  reply  to  Balfour's 
"■  Foundations  of  Belief  "  hastened  his  death,  which  came  upon 
June  29,  at  the  age  of  seventy. 

I  have  endeavored  to  show  in  how  many  ways  Huxley  was  a 
model  for  us  of  the  younger  generation.  In  the  central  hall  of 
the  British  Museum  of  Natural  History  sits  in  marble  the  life- 
size  figure  of  Charles  Darwin.  Upon  his  right  will  soon  be 
placed  a  beautiful  statue  of  Richard  Owen ;  and  I  know  that 
there  are  many  who  will  enjoy  taking  some  share  in  the 
movement  to  complete  this  group  with  the  noble  figure  of 
Thomas  Henry  Huxley. 


FOURTH    LECTURE. 


PALAEONTOLOGY    AS    A    MORPHOLOGICAL 
DISCIPLINE. 

PROF.    W.  B.    SCOTT. 
(Princeton  University,  Princeton,  N.J.) 

The  day  has  forever  gone  by  when  any  one  mind,  however 
profound  and  comprehensive,  can  take  all  knowledge  for  its 
province.  Increase  of  knowledge,  like  advance  of  civilization, 
necessarily  brings  with  it  a  division  of  labor,  and  each  of  the 
great  branches  of  science  becomes  more  and  more  minutely 
divided  and  subdivided  for  the  purposes  of  investigation.  Such 
subdivision  greatly  enhances  the  efficiency  of  the  individual 
worker,  enabling  him  to  concentrate  his  attention  upon  some 
definite  problem  of  more  or  less  limited  scope,  and,  so  far,  it  is 
advantageous.  On  the  other  hand,  like  most  human  devices, 
it  has  its  drawbacks,  and  what  is  gained  in  one  direction  is  apt 
to  be  lost  in  another.  One  great  and  growing  evil  is  the  sub- 
division of  knowledge  which  accompanies  specialization  of 
research.  The  worker  finds  the  greatest  difficulty  in  keeping 
abreast  of  all  that  is  being  accomplished  by  fellow  laborers  in 
his  own  field ;  how,  then,  shall  he  find  time  to  learn  anything 
of  the  work  in  other  fields }  Not  to  do  so  involves  the  penalty 
of  such  a  narrowness  of  view  as  will  inevitably  lessen  the  value 
of  his  own  work,  because  deductions  drawn  legitimately  enough 
from  a  single  line  of  investigation  often  appear  absurd  when 
tested  by  a  wider  range  of  facts.  Many  a  blunder  might  be 
avoided  were  the  worker's  vision  not  so  strictly  limited  by  the 
boundaries  of  his  own  speciality. 

The  narrowing  effects  of  this  subdivision  of  knowledge 
result  in  a  more  or  less  marked  loss  of  sympathy  and  mutual 


44  BIOLOGICAL   LECTURES. 

understanding  between  the  representatives  of  the  different 
branches  of  the  same  science.  To  magnify  one's  own  office  is 
a  very  human  infirmity,  but  it  involves  a  minimizing  of  the 
offices  of  others.  Science  is  not  advanced  by  the  sneers  of  its 
representatives  at  one  another  as  mere  ''  species-makers,"  or 
*' section-cutters,"  or  "closet-naturalists,"  as  the  case  may  be. 
One  is  prone  to  regard  with  instinctive  distrust  results  which 
run  counter  to  cherished  convictions,  or  which  ill  harmonize 
with  prevalent  theories  and  call  for  a  radical  readjustment  of 
opinion.  Naturally,  the  investigator  is  apt  to  place  undue 
reliance  upon  the  methods  with  which  he  is  familiar  and  to 
undervalue  other  ways  of  attacking  the  same  problem.  Evidence 
derived  from  other  lines  of  investigation  means  less  to  him  and 
is  the  more  readily  overlooked  and  ignored.  Perhaps  the 
greatest  danger  which  at  present  threatens  the  healthy  growth 
of  zoological  science  in  all  its  branches  is  the  ever-increasing 
tendency  to  ambitious  speculation,  founded  upon  the  narrowest 
basis  of  fact.  So  much  of  a  theoretical  taint  attaches  to  nearly 
all  morphological  work,  as  to  cause  hesitation  in  fully  accepting 
it,  and  one  often  feels  in  reading  that  we  have  gone  back  to 
the  days  of  the  transcendental  anatomists.  The  glib  use  of 
phrases  and  formulae,  which  hide  ignorance  under  the  guise  of 
"explanations"  which  do  not  explain,  is  an  outgrowth  of  the 
same  tendency.  It  is  the  fashion  to  measure  with  elastic  stand- 
ards, which  expand  and  contract  to  meet  the  needs  of  each 
case.  Dogmatism  and  narrow-mindedness  have  ever  been 
closely  akin. 

The  obvious  corrective  for  many  of  these  evils  is  to  take  a 
wider  view  of  our  subject,  and  for  each  of  us  to  learn  some- 
thing of  the  methods  and  results  of  workers  in  other  fields  than 
our  own.  I  wish  to  invite  your  attention  to  a  branch  of  mor- 
phology, the  bearings  of  which  are  much  misapprehended  by  the 
representatives  of  other  departments  of  the  same  science,  and 
which,  where  not  completely  ignored,  is  often  wofully  abused, 
namely,  the  subject  of  palaeontology.  This  science  has  too  long 
been  abandoned  to  the  geologist,  but  morphologists  are  coming  to 
see  that  they  have  an  interest  in  it,  and  sometimes  condescend 
to  make  use  of  such  parts  of  its  data  as  favor  their  opinions. 


PALEONTOLOGY  AS  A    DISCIPLINE. 


45 


Even  yet,  however,  the  necessary  and  close  connection  which 
obtains  between  palaeontology  and  geology  leads  many  to  the 
assumption  that  its  relation  to  morphology  is,  at  best,  very 
remote  ;  but  this  assumption  is  quite  unjustified,  and  proceeds 
from  a  confounding  of  the  two  quite  distinct  aspects  and  offices 
of  palaeontology.  One  of  these  offices  is  to  determine  the 
chronological  succession  of  the  rocks,  and  in  this  morphology 
is  very  indirectly  concerned  ;  but  the  other  office  is  the  study 
of  fossils  as  organisms,  and  here  Huxley's  dictum  thoroughly 
applies  :  "The  only  difference  between  a  collection  of  fossils 
and  one  of  recent  animals  is  that  one  set  has  been  dead  some- 
what longer  than  the  other."  This  is  a  shining  example  of  the 
**true  word  spoken  in  jest." 

The  great  problems  of  morphology  are  the  same  for  all 
workers  in  that  science  ;  it  is  the  method  of  attacking  them 
which  differs.  If  I  may  be  allowed  to  quote  what  I  have  else- 
where said,  I  would  again  call  attention  to  the  very  instructive 
character  of  the  analogies  which  exist  between  the  history, 
aims,  and  methods  of  animal  morphology  and  those  of  com- 
parative philology.  ''  In  both  sciences  the  attempt  is  made 
to  trace  the  development  of  the  modern  from  the  ancient,  to 
demonstrate  the  common  origin  of  things  now  widely  separated 
and  differing  in  all  apparent  characteristics,  and  to  establish 
the  modes  in  which,  and  the  factors  or  causes  by  which,  this 
solution  and  differentiation  have  been  effected.  At  the  present 
time  morphology  is  still  far  behind  the  science  of  language 
with  regard  to  the  solution  of  many  of  these  kindred  problems, 
and  can  hardly  be  said  to  have  advanced  beyond  the  stage  which 
called  forth  Voltaire's  famous  sneer:  "  L' Etymologic  est  une 
science  ou  les  voyelles  ne  font  rien  et  les  consonnes  fort  peu 
de  chose."  Of  the  animal  pedigrees,  now  so  frequently  pro- 
pounded, few  have  any  better  foundation  than  the  guessing 
etymologies  of  the  last  century,  and  for  exactly  the  same 
reason.  Just  as  the  old  etymologists  had  no  test  to  distinguish 
a  true  derivation  from  a  false  one,  except  a  likeness  in  sound 
and  meaning  in  the  words  compared,  so  the  modern  morpholo- 
gist  is  yet  without  any  sure  test  of  the  relationships  of  animals, 
except  certain  likenesses  or  unlikenesses  of  structure.     How 


46  BIOLOGICAL   LECTURES. 

much  weight  is  to  be  allowed  a  given  similarity,  and  how  far 
this  is  offset  by  a  dissimilarity  which  accompanies  it,  we  have, 
as  yet,  few  means  of  determining,  and  have  still  to  discover 
those  laws  of  organic  change  which  shall  render  the  same 
service  to  morphology  as  Grimm's  law  has  done  to  the  study  of 
the  Aryan  tongues." 

Philology  was  raised  to  the  dignity  of  a  true  science  by  the 
laborious  tracing  back  of  modern  words,  step  by  step,  to  their 
ancient  origins  through  all  their  intermediate  gradations,  and 
sound  principles  of  etymology  could  not  be  established  until 
this  was  done.  Morphology  must  profit  by  this  lesson  and 
must  imitate  the  method  of  the  science  of  language.  Not 
until  many  long  phylogenetic  series  have  been  recovered  can 
the  law  of  change  be  worked  out.  It  is  just  here  that  palae- 
ontology is  fitted  to  render  invaluable  services  to  the  common 
cause. 

As  every  one  is  aware,  the  principal  methods  of  morphological 
inquiry  are  comparative  anatomy,  embryology,  and  palaeon- 
tology, each  of  which  has  its  great  advantages,  but  accom- 
panied by  its  own  peculiar  drawbacks  and  limitations.  Lack 
of  time  will  prevent  any  discussion  of  Bateson's  proposed  new 
method  from  the  study  of  variation.  I  have  elsewhere  exam- 
ined that  at  some  length. 

The  foundation  and  corner-stone  of  the  whole  structure  of 
morphology  must  ever  be  comparative  anatomy,  an  accurate 
knowledge  of  which  is  indispensable  to  successful  prosecution 
of  the  other  departments  of  inquiry.  This  method  has,  in  the 
hands  of  the  masters,  registered  many  great  triumphs  in  the 
solution  of  difficult  problems  of  homology,  and  of  the  mutual 
relationships  of  animal  groups.  At  the  present  time,  the  ten- 
dency is  to  give  more  and  more  weight  to  its  determinations. 
On  the  other  hand,  finality  cannot  be  reached  by  this  method. 
It  suffers  from  the  very  significant  drawback  of  possessing  no 
sure  criterion  by  which  to  distinguish  between  those  similarities 
of  structure  which  result  from  actual  genetic  relationship  and 
those  which  are  due  to  parallel  or  convergent  development,  and 
thus  to  determine  the  taxonomic  value  of  a  given  likeness  or 
unlikeness.     It  is  an  exceedingly  common  fallacy  to  assume 


PALEONTOLOGY  AS  A    DISCIPLINE.  47 

that  because  a  number  of  allied  groups  display  a  certain  struc- 
ture, their  common  ancestor  must  also  have  possessed  it. 
This  may  have  been  the  case,  but  it  is  almost  as  likely  not  to 
have  been,  because  the  structure  in  question  may  have  been 
many  times  independently  acquired.  While  the  comparative 
method  frequently  enables  us  to  discriminate  between  the  two 
classes  of  phenomena,  it  generally  does  not  do  so,  and  it  never 
can  give  entire  certainty  upon  this  point. 

On  comparing  the  humerus  of  the  horses  with  that  of  the 
camels,  we  find  in  each  a  characteristic  difference  from  other 
artiodactyls  and  perissodactyls  and  agreement  with  each  other, — 
a  feature  which  may  be  described  in  brief  as  the  duplicity  of 
the  bicipital  groove  and  presence  of  a  bicipital  tubercle.  It  is 
a  priori  probable  that  such  an  isolated  resemblance  between 
two  widely  separated  groups  is  due  to  convergence,  and  yet 
the  comparative  method  can  give  us  no  assurance  that  this  is 
not  a  primitive  ungulate  character  retained  in  these  two  series 
and  lost  in  the  others.  Having  recovered  the  various  extinct 
genera  of  both  these  phyla,  we  may  trace  out  the  gradual  trans- 
formation of  the  humerus  and  definitely  show  that  the  resem- 
blance has  been  independently  acquired  at  a  comparatively  late 
period  and  is  not  a  case  of  a  persistent  primitive  feature. 

In  short,  the  difficulty  of  reaching  firmly  fixed  conclusions 
upon  questions  of  homology  and  relationship  by  the  exclusive 
use  of  comparative  anatomy  lies  in  the  fact,  that  this  method 
deals  only  with  the  modern  assemblage  of  animals,  a  mere 
fragment  of  that  which  has  existed  in  former  times.  It  is  like 
attempting  to  work  out  the  etymology  of  a  language  which  has 
no  literature  to  register  its  changes. 

The  second  method  of  morphological  inquiry,  embryology, 
has  had  a  somewhat  chequered  career.  Not  many  years  ago  it 
was  universally  regarded  as  the  infallible  test  of  morphological 
theory  and  the  principle  that  the  ontogeny  repeated  the 
phylogenetic  history  in  abbreviated  form  was  accepted,  almost 
without  question,  as  a  fundamental  law.  But  this  view  has 
fallen  somewhat  into  discredit.  The  admission  which  very 
early  had  to  be  made,  that  "  cenogenetic  "  features  of  develop- 
ment  were    imposed    upon    or   substituted   for   those  due  to 


48  BIOLOGICAL   LECTURES, 

ancestral  inheritance,  opened  the  door  to  an  unduly  subjective 
way  of  dealing  with  embryological  evidence  and  deprived  the 
method  of  that  authoritative  character  which  had  so  generally 
been  ascribed  to  it.  Now  the  whole  recapitulation  theory  is 
boldly  called  in  question,  and,  in  the  admirable  lecture  delivered 
last  year  in  this  place,  Prof.  E.  B.  Wilson  showed  the  untrust- 
worthy nature  of  the  embryological  criterion  of  homology.  The 
difficulty  in  this  case  lies  in  the  absence  of  any  "  canons  of 
interpretation "  (to  use  Bateson's  phrase)  by  which  the  con- 
tradictory data  of  embryology  may  be  harmonized  into  a  con- 
sistent whole.  To  take  a  concrete  illustration  :  The  ontogenetic 
development  of  the  horse's  teeth  would  give  us  a  very  inade- 
quate and  indeed  false  conception  of  the  actual  steps  of  change 
by  which  the  modern  type  of  dentition  has  been  attained,  nor 
would  embryology  show  that  the  horse  is  descended  from  five- 
toed  ancestors.  Knowing,  as  we  do  from  the  fossils,  the 
phyletic  series,  the  embryological  facts  may  be  readily  under- 
stood. It  is  an  undue  reliance  upon  such  facts  which  has  led 
to  the  concrescence  theory  of  tooth  development  now  so  rife 
in  Germany,  and  which  seems  so  absurd  when  viewed  in  the 
light  of  palaeontology. 

I  have  no  intention  of  belittling  the  splendid  services  which 
embryology  has  rendered  to  morphology,  but  merely  to  point 
out  that  this  method  alone  cannot  reach  finality  any  better 
than  comparative  anatomy.  It  resembles  dealing  with  a  lit- 
erature that  has  been  vitiated  by  many  forgeries,  only  the 
grossest  and  most  palpable  of  which  can  be  readily  detected. 

A  third  method  of  attacking  morphological  problems  is  that 
offered  by  palaeontology.  Let  us  begin  our  consideration  of 
this  method  by  frankly  acknowledging  its  drawbacks  and  limita- 
tions, (i)  In  the  first  place  there  is  the  imperfection  of  the 
geological  record.  Palaeontology  does  not  profess  and  never 
can  hope  to  reconstruct  the  whole  history  of  life  upon  the 
earth,  or  even  the  greater  part  of  that  history ;  very  many 
chapters  are  irretrievably  lost,  and  others  are  so  fragmentary 
that  they  teach  us  little  or  nothing.  The  great  sedimentary 
deposits  which  contain  nearly  the  whole  recorded  history  of 
the  globe  were  laid  down  under  water,  and  for  a  land  animal 


PALAEONTOLOGY  AS  A    DISCIPLINE.  49 

or  plant  to  be  entombed  there  is  a  lucky  accident.  If  all  we 
could  learn  of  the  terrestrial  life  of  North  America  had  to  be 
deciphered  from  the  fragments  enclosed  in  the  oceanic  deposits 
along  its  shores,  how  very  imperfect  would  our  knowledge  be  ! 
Although  the  estuarine,  swamp,  and  lake  formations,  which 
occur  on  such  a  grand  scale  among  the  rocks  of  the  earth's 
crust,  have  preserved  whole  chapters  in  the  history  of  terrestrial 
life  with  wonderful  fullness  and  accuracy,  they  are  all  too  few 
and  too  widely  separated  to  form  any  complete  record.  Even 
in  a  continuous  series  of  marine  deposits,  representing  vast 
periods  of  time,  there  are  sure  to  be  gaps  of  greater  or  less 
importance  in  the  record.  Changes  in  the  depth  of  water  and 
the  character  of  the  bottom  will  drive  out  one  set  of  forms 
from  that  locality  and  bring  in  another,  which  has  no  genetic 
connection  with  the  former,  which  may  perhaps  return  with  a 
renewal  of  the  old  conditions.  Many  groups  of  organisms  are 
incapable  of  preservation  in  the  fossil  state,  except  under  the 
rarest  conditions  —  conditions  which  occur  so  seldom  and  so 
widely  separated  in  space  and  time,  as  to  render  hopeless  any 
attempt  to  reconstruct  a  continuous  story  from  them. 

The  very  circumstances  under  which  organisms  are  preserved 
in  the  rocks  offer  another  obstacle  to  the  determination  of 
phyletic  series.  On  examining  large  collections  of  fossils  from 
several  successive  horizons,  we  find  that  the  majority  of  the 
species  and  even  of  the  genera  are  confined  to  one  or  two  for- 
mations, and  that  each  succeeding  fauna  is  recruited  partly  by 
migrations  from  other  regions  and  partly  by  the  rapid  expansion 
of  comparatively  few  adaptive  and  plastic  types,  while  most  of 
the  forms  which  were  especially  well  fitted  for  the  older  con- 
ditions die  out  under  the  new.  The  collections  are,  of  course, 
largely  made  up  from  the  abundant  and  dominant  species  of 
each  horizon,  which  frequently  are  not  the  ancestors  of  those 
which  will  be  dominant  in  the  succeeding  one.  The  sudden 
appearance,  as  it  so  often  seems  to  be,  of  a  fully  differentiated 
group  is  sometimes  due  to  that  cause,  sometimes  to  a  migration 
from  some  other  region.  Even  in  phyletic  series  which  are 
well-nigh  complete,  there  is  a  tendency  for  each  successive 
genus  to  undergo  similar  cycles  of  specific  variation  and  this 


50  BIOLOGICAL   LECTURES. 

adds  to  the  confusion,  the  very  completeness  of  the  record 
increasing  the  difficulty  of  its  interpretation. 

(2)  A  second  drawback  to  the  palaeontological  method  of 
inquiry  lies  in  the  incomplete  preservation  of  those  organisms 
which  are  fossilized.  Of  plants  we  find,  for  the  most  part, 
only  scattered  leaves,  rarely  the  reproductive  organs,  stems,  or 
roots,  and  often  the  proper  association  of  the  various  parts 
requires  the  strenuous  labor  of  years.  Of  animals,  except 
under  exceedingly  rare  circumstances,  only  the  hard  parts, 
teeth,  bones,  shells,  and  the  like,  are  preserved,  and  in  the  case 
of  vertebrates  how  seldom  is  even  the  skeleton  completely 
recovered  !  As  in  plants,  the  association  of  the  various  parts 
of  a  single  skeleton  may  require  the  long-continued  and 
laborious  efforts  of  many  workers.  Extraordinary  blunders 
have  sometimes  been  committed  in  this  work.  In  the  remark- 
able genus  Chalicotheriiim  the  skull  was  at  first  referred  to  one 
mammalian  order  and  the  feet  to  another,  and  Forsyth-Major's 
suggestion  that  they  all  belonged  together  was  received  with 
incredulity.  Of  the  even  more  curious  Agriochcenis  the  head 
was  ascribed  to  one  order,  the  fore-leg  to  a  second,  and  the 
hind-foot  to  a  third. 

The  utterly  false  notion,  which  nothing  seems  able  to  eradi- 
cate, that  the  palaeontologist  can  readily  restore  an  extinct 
type  from  a  single  bone  or  tooth,  ought  to  receive  its  quietus 
from  such  examples,  though  of  course  it  will  not.  It  is 
equivalent  to  saying  that  we  have  nothing  to  learn  from  the 
fossils,  and  that  all  possible  types  of  structure  are  exemplified 
in  the  living  world. 

On  account  of  this  incompleteness  of  preservation  we  cannot 
learn  much  that  we  wish  to  know  of  the  structure  of  extinct 
organisms.  The  nervous,  vascular,  muscular,  and  alimentary 
systems  are  entirely  lost  and  can  be  inferred  only  from  indirect 
and  often  insufficient  evidence.  Were  the  pearly  nautilus 
extinct,  our  notions  of  the  anatomy  of  the  tetrabranchiate 
cephalopods  would  be  very  much  astray,  and  in  the  cases  of 
several  groups  of  fossils  we  are  quite  unable  to  interpret  the 
structure  from  what  remains. 

(3)  A  third  difficulty  in  the  way  of  a  truly  morphological 


PALAEONTOLOGY  AS  A    DISCIPLINE. 


51 


palaeontology  consists  in  the  uncertainties  of  geological  cor- 
relation, by  which  the  relative  age  of  formations  in  widely 
separated  areas  and  different  continents  is  to  be  determined. 
It  may  and  often  does  make  a  vital  difference  in  the  construc- 
tion of  a  phylogeny,  whether  a  given  set  of  rocks  in  North 
America  is  older  or  younger  than  one  in  Europe,  with  which  it 
is  correlated.  The  principles  according  to  which  such  corre- 
lation is  to  be  made  are  still  somewhat  indeterminate,  and  not 
a  few  geologists  maintain  that  the  problem  is  an  insoluble  one. 
On  the  other  hand,  it  is  essential  to  the  palaeontologist  that  it 
should  be  solved,  and  already  a  very  encouraging  beginning 
has  been  made. 

(4)  In  the  fourth  place  the  apparent  order  of  succession  of 
organisms  in  the  stratified  rocks  must  not  be  too  implicitly 
and  uncritically  accepted.  Animals  and  plants  diffuse  them- 
selves as  widely  as  possible  until  stopped  by  some  impassable 
barrier.  During  the  long  ages  of  the  world's  history  these 
migrations  have  ever  been  in  progress,  and  they  greatly  confuse 
the  record  when  we  attempt  to  read  it  in  terms  of  evolutionary 
descent.  A  species  in  a  newer  formation,  which  appears  to  be 
derived  from  one  in  an  older  horizon  of  the  same  region,  may, 
as  a  matter  of  fact,  have  had  an  entirely  different  ancestry  and 
have  migrated  half  around  the  globe  to  the  place  where  it 
occurs.  To  make  these  distinctions  theoretically  is  easy,  to 
apply  them  very  difficult. 

(5)  Lastly  should  be  mentioned  a  practical  drawback  to  the 
palaeontological  method,  namely,  its  costliness.  The  naturalist 
may  find  much  to  do  in  other  departments  at  small  expense, 
which  will  be  a  source  of  infinite  pleasure  to  himself  and  of 
great  value  to  science.  Every  field  and  wood,  every  pond  and 
stream,  and  above  all  the  sea,  offer  boundless  stores  of  ma- 
terial. Even  the  side  of  palaeontology  which  bears  upon 
stratigraphy  and  historical  geology  may  be  taken  up  to 
great  advantage  by  the  private  worker  who  happens  to  live 
in  a  favorable  locality.  With  palaeontology  as  a  branch  of 
morphology,  however,  the  case  is  unhappily  very  different. 
Here  great  collections  brought  together  without  much  regard 
to  cost,  skilled  workers  to  prepare  the  specimens,  and  great 


52  BIOLOGICAL   LECTURES. 

buildings  in  which  to  house  them  are  indispensable.  Distant 
regions  must  be  examined  and  the  whole  world  ransacked  for 
material.  Many  problems  connected  with  the  North  Ameri- 
can fauna  must  await  their  explanation  until  Asia  can  be 
thoroughly  explored,  while  Africa  and  South  America  have 
already  shown  what  a  complete  geological  knowledge  of  those 
continents  may  be  expected  to  teach.  •  In  this  country  the 
arid  parts  of  the  West  have  yielded  a  marvelous  store  of 
wonderfully  preserved  fossils,  but  great  sums  have  been 
expended  in  gathering  them,  —  an  opportunity  which  falls  to  the 
lot  of  but  few.  It  is  to  be  hoped  that  the  multiplication  of 
museums  may  ere  long  put  within  the  reach  of  all  biological 
students  something  of  these  marvelous  stores  of  wealth. 

It  might  well  seem  that  all  these  limitations  and  drawbacks 
would  necessarily  disqualify  palaeontology  as  a  morphological 
subject  from  being  of  the  smallest  real  importance,  but  such  a 
conclusion  would  be  highly  erroneous.  Several  of  the  limita- 
tions are  but  partial,  not  applying  to  particular  cases,  while 
others  are  difficulties  that  further  investigation  may  hope  to 
remove,  not  insurmountable  obstacles.  Every  year  new  forms 
are  discovered  and  better  material  of  known  forms.  Though 
the  White  River  Bad  Lands  have  for  more  than  half  a  century 
been  classic  collecting  ground,  hardly  a  season  passes  that 
several  new  genera  are  not  registered  from  there,  and,  better 
still,  types  before  known  only  from  fragments  are  gradually 
made  more  and  more  complete.  From  the  middle  Eocene  to 
the  lower  Miocene  there  is  in  the  West  an  almost  unbroken 
transition  which  is  bringing  forth  a  truly  magnificent  series  of 
evolutionary  stages. 

While  palaeontology,  as  we  have  seen,  does  not  profess  to 
give  an  unbroken  life-history  of  the  earth,  yet  it  has  certain 
preeminent  advantages  which  neither  comparative  anatomy  nor 
embryology  possesses,  and  which  fit  it  to  form  an  invaluable 
supplement  to  those  other  methods  of  morphological  investiga- 
tion. 

(i)  In  the  first  place,  it  gives  us  in  many  cases  actual 
phyletic  series  in  their  true  order  of  succession  in  time.  In 
many  groups  of  animals  we  have  already  recovered    phyletic 


PALEONTOLOGY  AS  A    DISCIPLLWE. 


53 


series  so  full,  so  complete,  that  no  observer  can  hesitate  to 
accept  them  as  representing  actually  or  very  nearly  the  succes- 
sive steps  of  evolutionary  change  in  the  order  in  which  they 
occurred.  Little  confidence  may,  perhaps,  be  placed  in  these 
phyla  by  those  who  have  not  made  a  special  study  of  them, 
and  it  may  be  imagined  that  fuller  knowledge  will  require 
them  to  be  completely  changed.  But  when  we  find  such  a 
series  as  that  of  the  horses,  leading  back  by  almost  imper- 
ceptible gradations  from  the  great  monodactyl  living  forms  to 
their  little  five-toed  progenitors  in  the  far  distant  Eocene 
times,  doubt  becomes  well-nigh  impossible.  A  limit  of  error 
is  placed  by  the  stratigraphical  order,  the  geological  and 
morphological  successions  coinciding  beautifully.  Whatever 
changes  in  the  details  of  such  a  series,  a  radical  reconstruction 
of  it  is  not  in  the  least  likely  to  be  called  for.  Few  observers, 
if  any,  would  now  uphold  the  arrangement  of  the  equine 
phylum  proposed  by  Kowalevsky,  namely,  Palceotkeriiim, 
Anchitherhinty  Hipparion,  Eqtms ;  and  yet  it  is  surprising 
to  see  how  the  general  character  of  this  series  and  the  deduc- 
tions as  to  the  manner  of  evolution  which  may  be  drawn  from 
it  agree  with  those  made  on  the  basis  of  the  equine  series  as 
we  now  have  it.  Kowalevsky's  mistake  merely  consisted  in 
putting  certain  members  of  the  side  branches  into  the  main 
line  of  descent,  and  that  similar  errors  have  been  made  in 
accepted  phylogenies  is  not  at  all  unlikely.  The  correction  of 
such  errors  will,  however,  change  the  general  result  but  little, 
and  we  may  appeal  with  considerable  confidence  to  the  con- 
clusion which  legitimately  follows  from  a  study  of  these 
phylogenies. 

Fortunately,  the  well-defined  phyletic  series  which  have 
already  been  made  out  occur  in  very  widely  separated  animal 
groups,  —  mammals,  reptiles,  cephalopods,  brachiopods,  echino- 
derms,  etc.,  —  so  that  the  points  in  which  they  agree  are  apt  to 
prove  of  general  application  and  validity.  The  cephalopods 
are  particularly  valuable  in  this  connection,  because  in  them 
the  embryonic  and  young  stages  of  the  shell  are  preserved  in 
the  adult,  and  thus  conclusions  have  a  distinct  support  from 
embryological    considerations.      To    recur    to    the    linguistic 


54  BIOLOGICAL   LECTURES. 

analogy,  we  have  here  at  least  fragments,  and  sometimes  very 
extensive  ones,  of  the  various  literatures  which  register  the 
changes  of  language,  and  in  the  original  documents  which  bear 
evidence  of  their  dates  and  succession,  and  which,  however 
incomplete,  have  not  been  falsified  by  forgeries  and  late  inter- 
polations. In  this  way  we  may  establish  unequivocally  some, 
at  least,  of  the  animal  pedigrees,  which  it  is  one  of  the  great 
objects  of  morphology  to  construct,  and  thus  to  correct  the 
results  obtained  by  the  other  methods  of  inquiry.  Palaeon- 
tology further  enables  us  accurately  to  discriminate  between 
resemblances  which  are  due  to  genetic  affinity  and  those  which 
result  from  parallelism  or  convergence. 

To  illustrate  :  On  grounds  of  comparative  anatomy  Flower 
classified  the  land  Carnivora  into  three  sections  :  the  Cynoidea, 
or  dogs ;  the  Arctoidea,  containing  the  bears,  raccoons,  and 
mustelines  ;  and  the  Aeluroidea,  including  the  civets,  hyenas, 
and  cats.  This  classification  has  found  wide  favor  and  very 
general  acceptance,  but  palaeontology  shows  it  to  be  untenable. 
The  extinct  phyla  show  that  the  dogs  and  bears  are  very  closely 
akin,  as  are  the  mustelines,  civets,  and  hyenas,  while  the  cats 
occupy  a  very  isolated  position,  and  are  not  closely  allied  to 
any  of  the  other  families.  The  anatomical  characters  which 
suggested  Flower's  system  are  in  part  examples  of  conver- 
gence and  in  part  due  to  the  retention  of  primitive  characters 
in  some  groups  and  their  loss  in  others. 

Again,  reasoning  from  embryological  data.  Rose  and  others 
have  propounded  the  theory  that  the  complex,  multicuspidate, 
mammalian  tooth  has  been  formed  by  the  coalescence  of  many 
simple  teeth.  The  phyletic  series  enable  us  to  follow  the 
evolution  of  these  teeth  step  by  step,  and  demonstrate  the 
incorrectness  of  the  ''concrescence  theory."  In  fact,  the 
great  lesson  which  the  study  of  the  phyla  continually  brings 
home  to  the  observer  is,  that  trustworthy  results  are  to  be 
obtained  only  by  the  laborious  and  minute  tracing  of  the 
changes  through  every  step  of  the  way.  Fragmentary  series 
are  not  to  be  depended  upon,  and  the  wider  the  gaps  between 
their  members  the  more  uncertain  is  their  connection. 

(2)    The  reconstruction  of  pedigrees,  the  solving  of  homol- 


paljEontology  as  a  discipline.  55 

ogies,  the  determination  of  relationships,  and  the  estabhshing 
of  classification  upon  a  sound  and  natural  basis,  important  as 
these  are,  are  yet  only  a  part  of  the  great  task  which  mor- 
phology has  set  before  itself.  We  wish  to  penetrate  more 
deeply  into  the  mystery  of  nature,  and  learn  how  and  why 
these  changes  have  occurred ;  or,  in  other  words,  to  discover 
the  manner  in  which,  and  the  efficient  causes  by  which,  devel- 
opment is  effected.  On  these  subjects  there  is,  as  yet,  wide 
divergence  of  view  among  morphologists.  The  postulates  and 
assumptions  upon  which  morphological  discussions  are  founded 
are,  in  great  measure,  incapable  of  proof,  and  appeal  with  very 
different  degrees  of  force  to  different  minds.  Modes  of  devel- 
opment which  appear  axiomatic  to  one  observer  are  by  another 
regarded  as  absurd.  All  are  agreed  that  there  are  limits  to  the 
possibilities  of  change ;  no  one  attempts  to  derive  a  butterfly 
from  a  beetle,  or  a  horse  from  a  cow;  but  just  how  and  where 
these  limits  should  be  drawn  it  is  at  present  impossible  to  say. 
It  is  this  uncertainty  which  refers  the  question  to  the  individual 
judgment,  and  leaves  the  way  open  for  such  radical  differences 
of  opinion. 

To  the  solution  of  these  problems  of  evolutionary  modes 
palaeontology  offers  most  valuable  assistance,  drawn  from  the 
study  of  actual  phyla.  It  might  seem  that  this  was  merely 
arguing  in  a  circle,  because  the  construction  of  phylogenetic 
series  involves  certain  presuppositions  as  to  what  changes 
are  and  what  are  not  possible,  and  we  then  proceed  to  prove 
the  presuppositions  by  the  phyla  thus  constructed.  But  the 
cautious,  step-by-step  method,  guarded  by  the  order  of  appear- 
ance in  time,  offers  a  way  of  escape,  and  enables  us  to  con- 
struct phyla  in  harmonious  structural  and  stratigraphical 
succession,  which  must  very  nearly  represent  the  actual  stages 
of  change.  Only  a  beginning  has  been  made  in  this  work,  but 
the  results  drawn  from  an  examination  of  widely  separated 
phyla,  such  as  mammals,  gasteropods,  and  cephalopods,  are  so 
consistent  and  harmonious  as  to  be  full  of  promise  for  the 
future. 

Limitations  of  time  and  space  forbid  an  attempt  to  fully 
consider  here  all  the  deductions  which  have  been  suggested 


56  BIOLOGICAL   LECTURES. 

and  rendered  more  or  less  probable  by  this  method,  but  one  or 
two  principles  which  stand  out  with  especial  clearness  may  be 
mentioned. 

{a)  Evolution  is  ordinarily  a  continuous  process  of  change 
by  means  of  small  gradations.  The  continuous  character  of  a 
phylum  is  apt  to  be  proportional  to  the  relative  abundance  of 
its  representatives  in  the  strata,  which  is  equivalent  to  saying 
that  well-known  series  are  continuous,  while  apparently  dis- 
continuous series  are  imperfectly  known.  This  does  not  imply 
that  the  rate  of  change  was  always  uniform,  —  it  probably  was 
not,  —  or  that  a  sudden  alteration  of  conditions  may  not  bring 
about  discontinuity,  or  per  saltum  development.  It  means 
that  the  usual  and  normal  mode  of  advance  is  by  continuity 
of  change. 

ib)  Development  is,  in  most  instances,  direct  and  unswerv- 
ing. The  rise  of  new  forms,  and  the  decadence  and  degen- 
eration of  old  ones,  are  not  ordinarily  by  zigzag  and  meandering 
paths,  but  by  relatively  straight  ones ;  and  though,  of  course, 
a  path  once  taken  may  be  diverged  from,  yet  in  such  a  case  it 
is  not  regained.  This  applies  particularly  to  the  organism  as 
a  whole  ;  in  minor  details  more  latitude  is  permissible.  The 
evidence  is  not  yet  sufficient  to  show  just  how  widely  applicable 
this  principle  is. 

{c)  Parallelism  and  convergence  of  development  are  much 
more  general  and  important  modes  of  evolution  than  is  com- 
monly supposed.  By  parallelism  is  meant  the  independent 
acquisition  of  similar  structure  in  forms  which  are  themselves 
nearly  related,  and  by  convergence  such  acquisition  in  forms 
which  are  not  closely  related,  and  thus  in  one  or  more  respects 
come  to  be  more  nearly  alike  than  were  their  ancestors. 
While  some  observers  have  tacitly  or  explicitly  denied  the 
reality  of  these  processes,  most  authorities  have  been  com- 
pelled to  admit  them.  What  palaeontology  has  done,  and  is 
doing,  is  to  show  the  universality  of  these  modes  of  develop- 
ment, and  to  point  them  out  in  directions  where  they  had  not 
been  suspected.  To  give  a  few  examples.  The  crescentic,  or 
selenodont  molar,  has  been  separately  acquired  by  no  less  than 
three  groups  of  artiodactyls,  and  probably  others  as  well.     The 


PALAEONTOLOGY  AS  A    DISCIPLINE.  57 

spout-shaped  odontoid  process  of  the  axis  has  independently 
developed  in  the  horses,  the  tapirs,  and  in  three  artiodactyl 
series.  The  true  ruminants  (Pecora)  of  the  present  day  are, 
among  other  characteristics,  distinguished  from  the  remaining 
artiodactyls  by  the  hollow  tympanic  bullae,  which  in  the  pigs, 
tragulines,  and  camels  are  filled  with  cancelli,  or  spongy  bone. 
In  Oligocene  times  only  the  camels  had  acquired  the  cancelli ; 
the  other  groups,  though  already  differentiated  as  such,  still 
had  hollow  and  inflated  tympanies.  Lists  of  such  parallelisms 
in  single  characters  might  be  multiplied  almost  indefinitely, 
but  they  also  occur  in  whole  groups  of  structures.  The 
camels  have  in  teeth,  skull,  vertebrae,  and  limbs  many  points 
of  resemblance  to  the  true  ruminants,  which  demonstrably  are 
not  due  to  inheritance  from  a  common  ancestor.  The  two 
great  series  of  ungulates,  the  artiodactyls  and  perissodactyls, 
which  are  usually  grouped  together  as  the  Ungulata  par  excel- 
lence, are  examples  of  parallel  development  on  a  grand  scale, 
their  many  resemblances  being,  for  the  most  part,  independ- 
ently acquired.  The  flesh-eaters  known  as  Carnivora  include 
at  least  two,  and  probably  three  lines,  which  have  been  sep- 
arately given  off  from  the  primitive  flesh-eaters,  or  creodonts. 

Such  a  mode  of  development  greatly  increases  the  difficulty 
of  determining  phylogenies,  which  would  be  very  much  easier 
could  every  notable  resemblance  at  once  be  accepted  as  proof 
of  relationship.  It  often  renders  impossible  the  proper  classi- 
fication of  some  isolated  genus  which  seems  to  have  several 
incompatible  affinities.  It  emphasizes  the  necessity  of  found- 
ing schemes  of  classification  upon  the  totality  of  structure,  and 
of  determining  the  value  of  characteristics,  whether  they  are 
primitive  or  acquired,  divergent,  parallel,  or  convergent,  before 
attempting  to  assign  them  their  proper  taxonomic  value. 

We  may  find  a  practical  identity  in  teeth,  skull,  or  feet  as 
the  outcome  of  these  processes,  but  as  yet  no  case  is  known 
where  all  these  structures  have  become  alike  through  the  opera- 
tion of  either  parallel  or  convergent  development.  Among  the 
invertebrates  the  case  is  different.  Hyatt  has  shown  that  the 
degenerate,  straight-shelled,  ammonoid  genus  Baculites  is  a 
polyphyletic  group,  and  derived  from  several  distinct  stocks, 


58  BIOLOGICAL   LECTURES. 

both  European  and  American.  Wiirtenberger  points  out  that 
the  so-called  Ammonites  mutabilis  is  not  a  true  species,  but  a 
composite  group,  made  up  by  the  convergence  of  several  dis- 
tinct lines  to  a  common.  This  case  is  peculiarly  significant, 
because  it  would  hardly  have  been  detected  had  not  the 
embryonic  and  young  stages  of  the  shells  been  preserved. 

It  seems  the  most  obvious  of  commonplaces  to  say  that 
numerous  and  close  resemblances  of  structure  are  prima  facie 
evidences  of  relationship.  Yet  the  statement  is  true,  even 
though  the  resemblances  have  been  independently  acquired, 
because  parallelism  is  a  more  frequently  observed  phenomenon 
than  convergence,  and  because  the  more  nearly  related  any 
two  organisms  are,  the  more  likely  are  they  to  undergo  similar 
modifications. 

All  this  brings  us  back  to  the  thesis  so  frequently  insisted 
upon  already,  that  the  only  safe  and  trustworthy  method  of 
constructing  phylogenies  is  by  tracing  the  development,  step 
by  step,  through  all  its  gradations ;  and  until  this  is  done  the 
classification  of  any  group  can  be  but  tentative  and  provisional, 
that  is,  if  we  intend  classification  to  express  relationship. 

No  department  of  biological  science  is  at  present  the  scene 
of  such  vigorous  controversy  as  that  which  deals  with  the 
factors  of  evolution,  the  causes  which  determine  the  develop- 
ment of  new  forms,  and  the  problems  of  heredity  which  are 
inseparably  connected  with  them.  Palaeontological  evidence 
will  prove  to  be  of  much  importance  in  this  connection  also, 
but  it  cannot  well  have  more  than  a  corroborative  value. 
Though  the  examination  of  long  and  complete  phyla  brings  to 
light  much  that  is  suggestive  concerning  the  factors  which 
have  brought  these  changes  to  pass,  and  any  rational  theory 
must  embrace  and  explain  these  facts,  yet  the  deciding  weight 
must  probably  come  through  the  physiological  and  experi- 
mental method.  Time  fails  to  deal  with  such  far-reaching 
questions  here,  and  yet  it  may  be  well  to  call  attention  to  the 
necessity  of  avoiding  a  dogmatic  and  intolerant  attitude,  and 
to  deprecate  any  premature  attempt  to  exclude  this  or  that 
class  of  factors  from  consideration.  In  most  of  the  recent 
writings  upon  the  efficient  causes  of  evolution  you  will  find 


PALEONTOLOGY  AS  A    DISCIPLINE.  59 

expressed  or  implied  the  feeling  that  these  matters  are  not 
so  simple  and  intelligible  as  we  once  supposed,  and  that 
we  are  yet  only  upon  the  threshold  of  its  solution.  The 
study  of  palaeontology  will  not  tend  to  dispel  this  feeling  of 
mystery. 

Another  department  of  biological  science  in  which  palaeon- 
tology has  proved  of  great  value,  and  will  become  more  and 
more  so  in  the  future,  is  that  which  deals  with  the  geograph- 
ical distribution  and  migrations  of  organisms.  Though  not  a 
branch  of  morphology,  this  subject  has  a  very  significant 
bearing  upon  that  science,  and  cannot  be  ignored  in  any  com- 
prehensive theory  of  evolution.  This,  again,  is  too  large  a 
field  to  enter  upon  at  the  close  of  a  lecture.  It  must  suffice, 
therefore,  to  hint  at  the  many  cases  in  the  existing  distribu- 
tion of  animals,  which  seem  so  puzzling  and  capricious,  and 
which  are  so  readily  explained  by  a  study  of  the  past.  That 
the  nearest  allies  of  the  South  American  llamas  should  be  the 
camels  of  the  Old  World  seems  unaccountable  until  we  learn 
that  North  America  was  the  original  home  of  the  entire  tribe. 
The  occurrence  of  the  tapirs  in  South  America  and  in  the 
Malay  Peninsula  becomes  intelligible  enough  when  we  learn 
that  this  genus  is  of  very  high  antiquity,  and  was  formerly 
represented  in  every  part  of  the  northern  hemisphere. 

The  more  fully  the  past  is  recovered  the  more  completely 
the  former  land  connections  of  the  various  continents  are  made 
out,  the  more  comprehensible  do  the  seeming  anomalies  of  the 
present  order  of  things  become, — a  proposition  which  applies 
to  more  than  problems  of  geographical  distribution. 

The  foregoing  consideration  of  palaeontology  as  a  branch  of 
morphological  science  is  necessarily  brief  and  very  inadequate, 
but  it  will  suffice,  I  trust,  to  show  that  its  claims  upon  the 
attention  of  morphologists  should  not  be  ignored,  and  that  it 
is  admirably  fitted  to  throw  light  upon  many  obscure  problems. 
In  conclusion,  let  me  point  out  that  final  and  lasting  results 
are  not  to  be  gained  by  an  exclusive  adherence  to  any  method 
of  morphological  inquiry,  but  by  a  combination  of  all  of  them. 
Each  is  able  to  supplement  the  others,  and  it  is  folly  to  reject 
such  aid.     Already  most  encouraging  results   have   followed 


6o  BIOLOGICAL   LECTURES, 

from  this  combined  method  of  work,  and  it  is  devoutly  to  be 
wished  that  its  scope  may  be  more  and  more  extended.  As  an 
example  may  be  cited  the  recent  investigations  upon  the 
mammalian  dentition.  From  palaeontological  phyla  we  have 
learned  to  distinguish  the  homologies  of  the  cusps,  and  the 
way  in  which  a  complex  tooth  is  gradually  formed  from  a 
simple  one.  Embryology,  on  the  other  hand,  has  shown  the 
relations  of  the  successive  dentitions  to  one  another  in  a 
fashion  that  palaeontology  could  by  no  possibility  accomplish 
unaided.  As  another  example  may  be  mentioned  Wincza's 
discovery  of  a  bony  clavicle  in  the  embryo  of  the  sheep,  which 
was  soon  followed  by  the  still  more  unexpected  one  of  vestigial 
bony  clavicles  in  certain  extinct  artiodactyls,  confirming  and 
explaining  the  first.  Embryology  has  taught  us  that  the  large 
element  in  the  carpus  of  the  Carnivora  known  as  the  scapho- 
lunar  was  formed  by  the  coalescence  of  three  separate  bones, 
—  the  scaphoid,  lunar,  and  centrale.  Later  the  fossils  were 
unearthed,  which  showed  that  the  embryonic  and  transitory 
condition  of  the  modern  forms  was  the  permanent  and  adult 
structure  of  the  primitive  Eocene  flesh-eaters. 

The  more  the  combined  method  is  employed  the  more 
fruitful  does  it  appear.  Nor  should  the  combination  be 
restricted  to  the  technically  morphological  subjects.  Experi- 
mental embryology  has  already  won  some  notable  triumphs, 
and  that  is  a  physiological  quite  as  much  as  a  morphological 
province. 

In  the  ever-increasing  complexity  of  modern  civilization  a 
more  and  more  important  r61e  is  played  by  systematic  coopera- 
tion, specialists  combining  for  joint  work  which  neither  could 
accomplish  alone.  Is  it  Utopian  to  wish  that  some  such 
organized  scheme  of  attack  upon  biological  problems  shall 
be  devised,  when,  instead  of  every  man  doing  merely  that 
which  is  right  in  his  own  eyes,  we  shall  combine  in  a  definite, 
orderly  way  to  investigate  a  given  topic  in  all  its  bearings  }  It 
may  well  be  doubted  whether  any  naturalist,  however  great  his 
genius,  will  ever  again  be  able  to  take  such  an  exhaustive 
survey  of  biological  data  as  Darwin  did  in  his  time.  The 
enormous  mass  of   accumulated    facts   already  far  transcends 


PALEONTOLOGY  AS  A    DISCIPLINE.  6 1 

the  power  of  any  one  mind  to  grasp,  and  it  would  seem  that 
organized  cooperation  is  the  only  method  of  dealing  with  such 
vast  accumulations.  When  that  time  arrives  the  palaeontolo- 
gist will  be  able  to  render  even  more  conspicuously  valuable 
services  than  he  has  done  in  the  past. 


FIFTH    LECTURE. 


EXPLANATIONS,     OR      HOW     PHENOMENA     ARE 
INTERPRETED. 

BY  A.    E.   DOLBEAR. 
(Tufts  College,  College  Hill,  Mass.) 

How  long  a  time  mankind  has  been  on  the  earth  no  one 
knows.  When  I  was  a  lad  I  was  taught  that  the  earth  was 
made  about  six  thousand  years  ago.  Archbishop  Usher's 
chronology  was  accepted  by  all  except  a  few  geologists,  and 
their  conclusions  were  considered  as  speculative  vagaries,  in- 
vented by  men  whose  object  was  to  bring  the  Bible  into  dis- 
repute, and  against  whom  it  was  the  duty  of  men  who  loved 
the  truth  and  who  believed  they  possessed  it  to  warn  the  young. 
Now  it  is  believed  that  the  great  pyramid  of  Gizeh  has  been 
standing  for  nearly,  if  not  quite  as  long  a  time,  and  Egypt  was 
a  thickly  settled  country  with  well-established  government, 
laws,  customs,  religion  which  had  then  existed  for  a  long  time. 
Back  of  Egypt  was  Assyria  and  other  peoples,  and  farther  back 
still  other  peoples,  and  so  on  till  all  was  lost  in  an  antiquity 
reaching  back  probably  fifty  thousand  years  and  perhaps  twice 
that  period.  What  has  brought  about  the  change  in  opinion 
as  to  a  matter  of  that  character  which  cannot  be  rigorously 
demonstrated,  and  why  has  any  one  more  than  a  speculative 
interest  in  it  ?  The  answer  to  the  first  is  that  new  data  have 
been  found  bearing  upon  the  question  which  our  ancestors  did 
not  have,  and  a  necessity  was  felt  for  making  every  kind  of  testi- 
mony logically  consistent  with  every  other  kind.  To  the 
second,  one  must  say  that  every  thoughtful  person  who  is 
interested  in  his  own  existence  and  humanity  has  hopes  and 
fears  ;  he  is  aware  without  reasoning  upon  it  that  a  knowledge 


64  BIOLOGICAL   LECTURES, 

of  the  past  must  help  to  a  knowledge  of  the  future,  and  if  he 
can  properly  interpret  the  past  of  mankind  he  will  the  better 
know  what  to  anticipate  for  them  and  himself.  So  long  as 
creation  was  supposed  to  be  by  fiat  and  the  universe  to  have 
sprung  into  existence  just  as  Minerva  was  said  to  have  sprung 
from  the  brain  of  Jupiter,  there  was  no  trouble.  Everything 
was  satisfactorily  explained  by  saying  God  did  it.  The  ques- 
tion how  did  not  concern  any  one,  for  miracle  was  the  method 
of  deity,  and  needed  no  antecedent  but  the  will  of  the  deity. 
All  effort  was  given  to  establishing  the  authenticity  of  the 
biblical  record.  It  was  held  to  be  such  an  important  matter 
that  no  one  was  allowed  to  question  it,  or  assume  even  for  an 
instant  that  it  was  not  the  exact  truth.  The  importance  of  a 
knowledge  of  the  past  history  of  mankind  is  as  great  as  ever ; 
its  interest  has  not  abated  but  increased.  The  origin  and 
destiny  of  mankind  are  still  the  primal  questions,  and  all  knowl- 
edge in  any  department  of  human  effort  has  its  main  reason 
for  the  light  it  may  throw  on  these. 

In  this,  as  in  most  other  works,  there  are  two  ways  which 
men  have  adopted  to  satisfy  their  philosophical  wants.  One 
is  to  assume  what  is  thought  to  be  an  adequate  fundamental 
cause  or  principle,  a  mode  of  operation,  and  a  certain  logical 
process  also  believed  to  be  reliable,  and  with  these  to  construct  by 
a  deductive  process  the  observed  phenomena.  For  instance,  to 
account  for,  say,  the  Solar  system  as  it  appears  to-day.  Such 
a  philosopher  would  assume  first,  the  existence  of  a  deity  with 
the  attributes  of  omniscience,  omnipotence  and  will,  existing 
and  related  to  time  and  space  as  we  are.  Secondly,  he  assumes 
that  the  mode  of  operation  was  radically  different  from  any  he 
knows  of  or  can  imagine,  namely,  the  creation  of  both  matter 
with  all  its  qualities  and  also  energy  as  we  know  it,  for  we 
know  of  energy  only  as  existing  in  something  already  formed. 
And  thirdly,  he  assumes  with  these  that  he  may  trust  his  logi- 
cal process  and  reach  the  conclusion  that  the  existence  of  the 
Solar  system  and  everything  happening  in  it  is  properly  ex- 
plained by  assumptions,  neither  of  which  are  in  accordance 
with  human  experience.  For  first,  has  not  the  proof,  absolute 
proof,  of  the  existence  of  God  been  the  attempt  and  the  despair 


HOIV  PHENOMENA    ARE   INTERPRETED.  65 

of  philosophers  ?  If  we  possess  it  to-day  in  the  sense  that 
we  possess  proof,  —  say,  of  the  North  Pole  or  the  existence  of 
the  ether  of  space,  —  where  is  it  to  be  found  ?  Proof  of  the 
latter  compels  assent  as  soon  as  perceived,  yet  every  one  feels 
there  is  something  desirable  lacking  in  the  former.  It  may  be 
more  or  less  probable,  but  certainty  is  what  we  are  talking 
about. 

Again,  creation  implies  a  process  by  which  nothing  becomes 
something.  If  the  matter  which  constitutes  the  world  was 
simply  formed  out  of  something  else  which  was  not  matter, 
then  it  is  that  something  else  we  are  concerned  about,  and  the 
inquiry  properly  belongs  to  that  antecedent  something.  Now 
all  of  our  experiences  in  any  field  are  with  matter  and  with 
forms  of  energy.  Experience  with  the  former  has  led  to  the 
conviction  that  its  quantity  is  not  changed  in  the  slightest 
degree  by  any  kind  of  a  physical  or  chemical  process.  Once  it 
was  thought  possible  to  change  lead  to  gold,  but  it  was  in  the 
prescientific  age  when  chemical  products  were  not  weighed  in 
the  balance,  and  the  spectra  of  the  elements  had  not  been  seen. 
Experience  with  energy  has  led  to  the  formulation  embodied 
in  the  doctrine  of  the  Conservation  of  Energy,  namely,  that 
the  quantity  of  energy  in  the  universe  is  constant.  No  kind 
of  changes  alters  the  quantity.  If  these  deductions  from  expe- 
rience be  true,  it  follows  that  either  what  we  call  matter  and 
energy  have  always  existed,  or,  if  either  had  a  beginning,  it 
must  have  been  by  some  process  out  of  all  relation  to  every- 
thing we  know,  —  one  which  can  neither  be  described  nor 
imagined,  and  explanation  is  therefore  impossible,  if  explana- 
tion means  what  we  mean  by  it  when  applied  to  such  a  process 
as,  say,  the  generation  of  electricity  in  a  dynamo ;  for  in 
this  we  have  definite  known  antecedents  of  steam  power,  heat, 
and  so  on.  In  experience  we  have  only  transformations,  all 
of  which  imply  matter  as  the  condition  of  transformations. 
The  creation  of  energy  is  a  radically  different  affair,  and  it 
is  a  fair  question,  by  what  warrant  does  any  one  assume  a 
process  wholly  foreign  to  experience  as  a  basis  of  a  philos- 
ophy of  experience  ? 

Again,  the  fallibility  of  human  logic  has  been  so  many  times 


66  BIOLOGICAL   LECTURES. 

shown,  and  in  so  many  different  fields  when  applied  in  cases 
where  verification  has  been  possible,  that  one  may  well  hesitate 
about  holding  very  fast  to  any  conclusion  which  has  not  yet 
been  adjudicated  by  experience.  This  holds  as  true  for  what 
we  call  philosophy  as  for  science.  We  are  in  possession  of  a 
body  of  scientific  doctrines  or  propositions  about  material 
phenomena  which  are  satisfactory  to  this  extent  :  they  have 
met  all  the  criticism  to  which  they  have  been  subject  by  men 
of  every  nation  who  have  concerned  themselves  with  them. 
Such,  for  instance,  are  the  doctrines  of  mathematics,  of  astron- 
omy, of  geology,  and  some  others  in  physical  science,  all  of 
which  deal  with  verifiable  matters,  that  is,  with  matter  and  the 
forms  of  energy  and  their  relations.  In  gaining  this  degree  of 
certainty  there  has  been  a  series  of  steps  taken  tentatively, 
engrossing  the  attention  of  men  interested  in  science  for  a 
century  or  two.  The  thing  to  note  here  is,  that  obvious  as 
many  of  these  propositions  are  to  us,  now  they  are  pointed  out, 
they  were  so  far  from  obvious  to  our  predecessors  that  almost 
every  other  conjecture  was  entertained,  and  often  with  no 
attempt  at  verification  before  the  present  ones  were  adopted. 
This  is  of  so  much  importance  that  some  examples  may  be  use- 
ful to  make  plain  the  meaning.  Take  the  case  of  the  explana- 
tion of  the  position  and  motions  of  the  earth,  and  other  bodies. 
First,  as  to  the  center  of  creation  about  which  sun,  moon,  and 
stars  revolved.  The  apparent  was  taken  to  be  the  truth,  and 
the  difficulties  of  such  an  explanation  of  the  apparent  were 
quite  ignored,  and  the  necessity  of  having  some  sort  of  an 
answer  to  the  question  as  to  the  causes  of  day  and  night  was 
so  great  that  such  an  explanation  was  thought  to  be  better 
than  nothing.  After  that  came  Ptolemy's  explanation,  a  w^on- 
derful  and  intricate  system  of  cycles  and  epicycles  which 
mechanically  would  not  work,  but  served  for  a  time  better  than 
the  one  it  displaced.  Then  came  Copernicus  with  the  plan  of 
the  sun  as  the  center  with  the  planets  and  the  earth  revolving 
about  it.  This  simplified  the  problem,  but  the  reason  given 
for  supposing  the  orbits  of  the  earth  and  the  planets  to  be 
circular  was  not  a  physical  reason, — that  is,  not  an  observed 
or   calculated    one,  but  a  metaphysical    reason  ;    that    is,  one 


HOW  PHENOMENA    ARE   INTERPRETED.  67 

which  was  imagined  to  be  in  accordance  with  moral  quality. 
The  Almighty  had  made  things  perfect ;  a  circle  was  the  only 
perfect  circuit.  Kepler  discovered  that  none  of  the  bodies 
involved  moved  in  circles  but  in  ellipses,  and  this  is  known  as 
one  of  Kepler's  laws.  But  Kepler,  unable  to  imagine  how 
such  bodies  could  move  in  such  ellipses  as  he  observed  they 
did,  and,  like  others,  feeling  obliged  to  give  some  sort  of  an 
explanation  for  the  apparent  anomaly,  invented  guiding  spirits 
whose  office  was  to  thus  move  the  heavenly  bodies.  Then 
came  Sir  Isaac  Newton,  who  showed  that,  with  gravitation 
assumed,  all  the  observed  motions  were  accounted  for,  and 
further,  that  the  so-called  perfect  circle  orbit  was  the  only 
unstable  orbit. 

In  this  series  of  steps  towards  the  explanation  of  observed 
phenomena,  the  first  was  wrong  in  every  particular.  The 
others  were  wrong,  and  wholly  wrong,  to  just  the  extent  they 
departed  from  simple  mechanical  relations  and  incorporated 
unmechanical  and  unrelated  notions  with  their  explanations. 
Again,  it  has  been  thought  a  reasonable  explanation  of  the 
relations  and  motions  of  the  bodies  which  make  up  the  Solar 
system  that  they  were  thus  created,  each  one  at  its  proper  dis- 
tance from  the  sun,  and  with  rotations  and  revolutions  properly 
adjusted  for  stability.  The  Solar  system  started  thus.  No 
reason  or  explanation  was  needed  save  that  it  was  the  will  of 
an  omnipotent  creator  which,  as  already  pointed  out,  is  not  an 
explanation  but  a  reference  to  the  unexplainable.  Kant  per- 
ceived that  the  involved  relations  were  probably  of  a  mathe- 
matical sort,  and  inferred  there  was  probably  some  simple 
mechanical  explanation  of  the  whole  arrangement.  Laplace 
attacked  the  problem  and  showed  if  the  material  which  now 
makes  up  the  Solar  system  had  been  scattered  in  space  in  a 
gaseous  form,  gravitation  would  bring  it  to  just  such  a  system 
of  globes,  with  masses,  distances,  rates  of  rotation  and  satellites 
as  we  find  them  to  have.  The  telescopes  at  that  time  showed 
many  patches  of  nebulous  masses  in  the  sky ;  but  as  the  tele- 
scope was  improved  many  of  these  patches  were  seen  to  be 
dense  clusters  of  stars,  and  the  inference  was  fairly  allowable 
that  with  sufficient  telescopic  power  all  might  in  a  similar  way 


68  BIOLOGICAL   LECTURES. 

be  resolved.  The  spectroscope,  an  instrument  for  determining 
whether  matter  is  solid  or  gaseous,  when  turned  towards  the 
sky  showed  that  there  were  vast  numbers  of  gaseous  masses 
there  and  in  many  degrees  of  condensation.  This  discovery 
was  held  to  corroborate  the  idea  of  Kant  and  Laplace,  so  that 
to-day  there  is  no  astronomer  who  does  not  hold  the  view  that 
the  Solar  system  as  we  see  it  to-day  is  a  growth,  that  it  was 
not  made  as  it  is,  and  that  gravity  with  the  simple  laws  of 
motion  are  sufficient  in  themselves  to  organize  the  Solar 
system  as  we  find  it,  and  an  explanation  of  it  is  an  exposition 
of  how  these  factors  brought  it  about. 

The  distribution  of  land  and  water,  mountains,  valleys,  rocks 
and  their  contents  in  like  manner  were  held  to  be  explained  by 
the  statement  that  they  were  thus  created  substantially  as  we 
find  them.  When  it  was  noted  that  animal  and  vegetable 
remains  were  to  be  found  in  abundance  in  many  rocks,  very 
little  thought  was  needed  to  induce  the  question  :  If  these 
rocks  have  been  in  place  from  the  beginning,  how  came  they 
to  be  filled  with  evidences  of  marine  life  such  as  fossils  attest  } 
Did  the  ocean  once  cover  the  mountain  tops  }  Once  the 
attempt  was  made  to  explain  their  presence  by  reference  to 
Noah's  flood  which  was  held  to  have  covered  mountain  tops, 
but  the  fossils  were  to  be  found  through  great  rock  formations 
and  through  rock  depths  of  miles.  It  was  noticed  presently 
that  the  lower  formations  had  simpler  forms  and  the  lowest 
rocks  none  at  all.  There  was  but  one  meaning  to  all  this, 
namely,  the  surface  of  the  earth  had  been  depressed  and 
elevated  above  their  present  level,  that  the  ocean  must  have 
once  covered  what  is  now  a  mountain  chain.  It  was  also  noted 
that  slow  changes  in  elevation  are  now  going  on  in  many  places. 
The  coast  of  France  is  sinking,  the  coast  of  Norway  rising. 
The  temple  of  Jupiter  Serapis  has  twice  been  submerged  in 
the  Mediterranean  Sea  and  is  now  out  of  water.  The  Missis- 
sippi River  is  building  shores  in  the  Gulf  of  Mexico  at  the  rate 
of  a  mile  or  two  a  year  with  the  detritus  brought  from  the 
central  valleys  of  the  United  States,  and  Niagara  Falls  is 
retreating  at  the  rate  of  a  foot  or  two  a  year.  Such  phenomena 
imply  unstable  land  and  water  surfaces.     The  physical  features 


HOIV  PHENOMENA    ARE   INTERPRETED.  69 

of  the  earth  are  changing  slowly.  In  time  they  can  change 
to  an  unlimited  extent.  Geologists  explain  all  geologic  phe- 
nomena as  due  to  physical  causes  such  as  are  now  going  on  ; 
but  the  implication  is  that,  given  simply  time,  everything 
we  observe  of  this  character  is  easily  understood,  —  with  no 
appeal  to  other  than  such  factors  as  are  at  work  before  our 
eyes,  —  and,  with  such  a  background  as  is  afforded  by  an  appeal 
to  astronomy,  there  is  good  reason  for  holding  that  no  other 
physical  factors  than  the  ordinary  type  have  been  involved  in 
the  geologic  phenomena.  Geological  facts  are  explained  by 
presenting  their  physical  antecedents,  and  the  explanation  stops 
when  traced  to  these,  that  is  to  say,  when  in  the  territory  of 
astronomy  or  physics. 

Once  more :  only  a  generation  ago  men  believed  that  all 
species  of  animals  and  plants  upon  the  earth  were  descended 
from  similar  forms  without  modification  from  the  original  ones 
created  by  fiat.  The  horse  of  to-day  is  like  his  ancestor  of 
thousands  of  years  ago,  the  lily  like  the  original.  In  like 
manner  all  plants  and  animals  and  men  represented  in  form 
and  qualities  their  prototypes.  Not  because  any  one  had  ever 
been  a  witness  to  such  a  process  of  creation  nor  because  there 
were  other  evidences  which  deserved  attention,  but  it  was  a 
kind  of  habit  of  mind  to  pretend  to  explain  phenomena  by 
referring  to  some  inexplicable  process  out  of  all  relations  with 
experience.  In  1846  a  book  was  published  anonymously,  called 
Vestiges  of  Creation.  It  attempted  to  show  that  all  the  present 
forms  of  life  might  have  resulted  from  the  simplest  forms  of 
life  by  a  series  of  small,  almost  insensible  changes  in  the 
organisms,  if  these  were  continued  for  a  great  number  of 
generations.  The  idea  was  condemned  by  almost  everybody 
interested  in  the  question,  not  from  defective  evidence,  but 
simply  because  it  required  the  abandonment  of  a  belief  that 
had  not  a  particle  of  evidence  in  its  favor.  That  is  to  say,  an 
attempted  explanation  which  had  much  experience  in  its  favor 
was  rejected  by  theologians  and  naturalists  alike,  and  another 
explanation,  having  not  a  particle  of  evidence  and  no  degree  of 
probability,  was  held  to.  Since  the  time  of  Darwin  all  that 
has  been  changed.     The  view  advocated  in  Vestiges,  though  not 


JO  BIOLOGICAL   LECTURES. 

with  such  conclusiveness  as  by  Darwin,  has  been  generally 
adopted  by  naturalists  of  every  nation. 

To  accept  Darwin  is  to  accept  the  proposition  that  there 
never  was  a  first  horse  or  first  rose  or  first  man.  The 
ancestry  of  the  horse  has  been  traced  back  through  a  long 
series  of  forms  as  far  as  an  extinct  animal,  known  in  zoology  as 
the  paleotherium,  which  was  no  more  like  a  modern  horse  than 
is  a  tapir;  but  this  distant  animal  may  have  been  extinct  for  a 
million  years  or  more.  No  matter  how  long  now,  the  point  is 
that  the  old  notion  has  been  given  up,  and  appeal  has  been 
^made  for  all  changes  in  form,  size,  habits,  and  adaptations  to 
processes  now  going  on,  and  all  appeal  to  other  or  superphysical 
agencies  has  been  abandoned  by  naturalists  of  every  country. 
This  means  that  in  such  important  matters  as  the  phenomena 
of  living  things  there  is  felt  to  be  no  necessity  for  going 
beyond  ordinary  factors  operating  to-day,  in  precisely  the  same 
sense  as  was  the  case  of  geology  and  astronomy.  The  expla- 
nations accord  with  experience,  and  exposition  is  only  the  pre- 
senting of  factors  and  conditions  in  their  proper  order.  The 
explanations  in  each  of  these  are  adequate  only  when  the  ante- 
cedents are  sufficiently  well  known  to  make  it  plain  they  need 
no  supplementary,  unrelated  factors. 

We  hear  in  these  days  of  the  forces  of  nature,  of  heat,  of 
light,  of  electricity,  and  the  latter  especially  is  popularly  con- 
sidered as  a  very  mysterious  something  which  nobody  can 
understand.  These  factors  are  supposed  to  act  upon  matter 
and  compel  it  to  do  this  or  that,  go  here  and  there.  Heat  in 
the  old  books  was  often  called  caloric,  and  that  was  supposed 
to  be  an  imponderable  something  which  could  now  be  in  matter 
and  now  out.  When  in  it,  it  caused  the  matter  to  exhibit 
certain  kinds  of  phenomena;  when  it  was  out,  none  inquired  as 
to  where  it  was  or  what  it  was  about.  During  this  century  it 
has  been  conclusively  proved  that  heat  is  but  a  particular  kind 
of  motion.  When  one  body  strikes  another  body  it  imparts 
some  of  its  motion  to  it  for  mechanical  reasons,  and  if  a  body 
possessing  heat  motion  comes  in  contact  with  another  body 
having  less  of  that  kind,  it  imparts  some  of  that  heat  to  it. 
What   one  loses  the   other   gains.     There  has   been   nothing 


HOW  PHENOMENA    ARE   INTERPRETED.  71 

more  mysterious  than  an  exchange  of  motion ;  there  is  no 
imponderable  substance  to  be  now  in  and  now  out,  —  only  a 
change  in  the  conditions.  Taking  this  view  of  heat  it  is  easy 
to  see  that  the  terminology  served  to  mislead  thinking ;  but  the 
view  here  presented  shows  that  heat  cannot  be  properly 
called  a  force  any  more  than  the  vibrations  of  a  bell  or  a  piano 
string  can  be  called  a  force,  and  so  heat  is  out  of  the  category 
of  force. 

Light  was  also  an  imponderable  substance.  Now  we  know 
it  to  be  wave  motion  in  the  ether,  and  the  vibrations  that  con- 
stitute the  heat  of  molecules  set  up  these  waves  in  the  ether, 
and  the  latter  conducts  them  away  at  the  high  rate  of  186,000 
miles  a  second.  The  heat  motions  are  the  antecedents  of  the 
light  motions  in  the  ether  in  every  case,  and  every  ray  of  light 
when  traced  back  to  its  source  ends  in  a  vibrating  molecule. 
So  if  heat  be  not  a  force,  neither  can  light  be  so  considered, 
and  two  of  the  imponderables  are  gone  as  forces. 

Electricity  as  another  wonderful  force  is  known  to  originate 
in  the  motions  of  molecules,  for  both  by  chemical  action  and 
by  heat  action  it  is  produced.  It  also  disappears  when  allowed 
to  do  either  chemical,  thermal,  or  mechanical  work.  As  it  has 
molecular  motion  for  its  antecedent  and  molecular  work  for 
its  resultant,  it  follows  that  its  nature  cannot  be  materially 
different  from  that  of  the  others.  Indeed,  so  well  established 
are  these  interrelations  between  heat  and  electricity  that  large 
industrial  enterprises  are  founded  upon  them.  The  point  here 
is  that  electricity,  as  an  independent  something, — a  force  that 
may  be  summoned  like  an  Afrite  in  The  Arabian  Nights  to  do 
duty  for  a  while  and  then  be  dismissed  from  service  to  be  no 
one  knows  where,  —  is  an  idea  wholly  wrong.  It  is  a  condition, 
not  a  thing,  for  electrical  energy  may  be  wholly  transformed 
into  heat  energy  or  into  light  or  other  kinds  of  work.  So  far 
we  have  only  matter  and  forms  of  motion  in  matter,  and  forces 
as  such  have  no  existence.  And  if  this  be  true  it  will  be  well 
to  abandon  the  notion  of  either  of  these  agencies  as  forces  or 
things  having  an  existence  apart  from  matter.  There  is  no 
evidence  for  such  a  view,  and  any  quantity  of  evidence  against 
it.     The  explanation  of  the  phenomena  due  to  either  or  all  of 


72  BIOLOGICAL   LECTURES. 

them  requires  nothing  beyond  the  factors  I  have  already  named, 
and  there  is  no  need  of  assuming  anything  more  mysterious 
than  these.  If  all  phenomena  in  the  realm  of  the  so-called 
inorganic  nature  be  due  to  matter  and  its  various  motions, —  and 
of  this  there  seems  to  be  little  reason  to  doubt,  and  no  one 
argues  otherwise,  —  then  what  is  the  use  of  talking  about  forces 
of  any  kind,  seeing  they  have  no  existence.  How  much  differ- 
ence this  will  presently  make  in  one's  conceptions  any  one 
may  discover  by  omitting  the  use  of  the  word  ''force "  from 
his  vocabulary  for' a  day  or  two,  whenever  he  discourses  and  at- 
tempts an  explanation  of  a  phenomenon.  It  will  be  perceived 
that  the  word  is  used  generally  as  a  pretentious  substitute  for 
ignorance. 

Living  things,  both  plants  and  animals,  were  thought  for  a 
long  time  to  be  endowed  with  a  quality  radically  different  from 
inanimate  things.  The  processes  of  digestion,  assimilation, 
growth,  and  the  like  were  believed  to  be  dependent  upon  a 
peculiar  agency  capable  of  dominating  the  ordinary  chemical 
activities  which  otherwise  would  destroy  the  organism.  This 
was  called  vital  force.  Organic  chemistry  was  the  name  given 
to  the  processes  by  which  a  host  of  complex  compounds  were 
formed  in  living  things,  and  vital  force  was  credited  with  being 
the  agency  in  all  of  them.  By  and  by  a  chemist  succeeded  in 
producing  in  an  artificial  way  a  single  one  of  these  products, 
and  the  announcement  was  a  stunner  to  both  physiologists  and 
chemists.  Soon  other  chemists  found  artificial  ways  of  making 
others,  and  to-day  so  great  a  number  have  been  produced  in 
the  laboratory  that  chemists  do  not  hesitate  to  express  their 
belief  that  every  organic  substance,  even  protoplasm,  may  thus 
be  formed,  and  that  also  in  the  animal  body  there  is  no  such 
agency  at  all  as  was  called  vital  force.  Physiologists  trace 
physiological  phenomena  without  exception  to  the  activities  of 
ordinary  forms  of  energy  known  as  physical  and  chemical,  not 
because  chemists  have  been  able  to  build  up  all  compounds 
known,  but  because  among  the  tens  of  thousands  which  have 
been  thus  formed  there  is  nothing  more  required  than  what 
can  be  provided  in  a  test  tube  ;  and  also  because  it  has  been 
fairly  well  proved  that  there  is  a  direct  and  quantitative  rela- 


HOIV  PHENOMENA    ARE  INTERPRETED.  73 

tion  between  the  energy  of  food  and  bodily  activity  of  every 
kind ;  that  no  more  comes  out  of  the  bodily  machine  in  the 
shape  of  work,  physical  or  mental,  than  is  physically  provided 
by  the  foods  digested.  So  vital  force  as  an  agency  in  living 
things  is  as  mythical  as  the  other  forces  I  have  described  as 
non-existent.  An  explanation,  then,  of  the  phenomena  of  life 
as  manifested  in  either  plant  or  animal  is  complete  when  the 
physical  and  chemical  antecedents  have  been  presented  in 
their  order  and  quantitative  relations.  There  appears  to  be  no 
reason  for  holding  to  the  view  that  there  is  anything  more 
mysterious  or  different  in  kind  in  so-called  vital  phenomena 
than  there  is  in  what  goes  on  in  a  test  tube  in  a  physical 
laboratory.  There  may  be  a  difference  in  complexity,  not  in 
agencies. 

Of  course  everybody  knows  of  what  is  called  the  conserva- 
tion of  energy  which  implies,  as  I  have  said  already,  that  the 
quantity  of  energy  in  the  universe  is  constant,  and  when  any 
given  kind  appears,  it  is  always  at  the  expense  of  some  other 
kind  which  has  disappeared,  and  the  two  are  equal.  If  the 
quantity  of  matter  is  not  variable, — and  that  is  precisely  what 
all  experience  affirms, — and  if  the  quantity  of  energy  is  also  not 
variable,  though  its  forms  may  be,  then  the  apparent  logic  of 
the  case  is  that  one  of  the  factors  of  energy  must  be  the 
variable,  and  in  fact  energy  as  we  know  it  is  always  a  product. 
It  does  not  exist  as  an  entity.  One  cannot  assume  that  the 
energy  of  a  moving  rifle  bullet  can  be  detached  from  it,  so 
as  to  enable  one  to  hold  the  bullet  in  one  hand  and  the  energy 
in  the  other.  The  variable  factor  is  simply  the  rate  of  motion 
the  bullet  may  have,  and  this  rate  of  motion,  whatever  it  may 
be  in  a  given  case,  had  its  antecedent  in  some  other  body  which 
lost  the  motion  which  was  imparted  to  the  bullet.  If  this  be 
applied  in  every  case,  then  it  seems  that  every  kind  of  phenom- 
enon involving  physical  energy  —  and  every  phenomenon  does 
involve  such  energy  —  must  be  due  to  changes  in  the  kind  and 
direction  and  amount  of  motions  a  body  may  have  ;  and  there  is 
no  reason  for  imagining  or  supposing  in  any  given  case  the 
existence  or  activity  of  any  agency  differing  from  or  related 
to  those  forms  of  energy  which  are  investigated  in  physical 


74  BIOLOGICAL   LECTURES. 

science.     Forces  dethroned,  and  matter  indestructible, — that  is 
the  result  of  the  scientific  activity  of  the  past  half  century. 

When  one  contemplates  that  proposition,  and  thinks  of  the 
wonderful  variety  of  phenomena  in  the  earth  and  in  the 
heavens,  and  then  attempts  to  realize  even  in  a  faint  way  how 
all  this  can  possibly  come  about  through  the  sole  agency  of 
motions  of  any  kind,  however  complex  in  their  combinations,  he 
cannot  but  feel  there  must  somehow  and  somewhere  be  an 
undetected  slip  in  the  logic,  or  there  must  be  a  factor,  and  a 
most  important  factor,  left  out ;  for  at  some  time  in  the  history 
of  things,  at  any  rate  on  the  earth,  there  have  appeared  not  only 
living  things  as  plants  and  animals,  but  activities  of  another 
class,  feelings  and  intelligence.  Along  with  physical  happen- 
ings and  physical  things  there  has  come  the  senses  and  the 
intellect,  the  possibility  of  pleasure,  the  consciousness  and 
delight  in  existence,  hopes  and  fears,  and  other  phenomena, 
which  cannot  by  any  jugglery  of  idea  or  language  be  resolved 
into  molecular  vibrations  or  rotations,  or  any  other  motions 
whatever.  They  are  the  things  we  live  for,  and  care  to  live 
for.  These  qualities  we  find  in  experience  to  be  always  associ- 
ated with  matter  and  various  forms  of  energy;  but  the  character 
of  the  two  classes  of  phenomena  appears  so  different  as  to  have 
led  philosophers  to  the  conclusion  that  they  could  exist  apart, 
having  no  necessary  relation  to  each  other ;  indeed,  the  terms 
"  matter  "  and  "  mind  "  are  generally  set  against  each  other  as 
contrasting  things  which  have  nothing  in  common.  Matter 
has  been  called  dead,  inert,  and  incapable  of  doing  anything 
except  when  other  agencies  as  forces  have  acted  upon  it,  while 
mind  has  been  believed  to  be  the  source  of  life  and  endowed 
with  inherent  energy.  What  is  energy }  The  books  do  not 
make  it  clear.  To  say  it  is  ability  to  do  work  is  not  to  define 
it,  but  to  tell  what  it  can  do.  Wind,  water,  steam,  electricity, 
a  horse  may  do  work,  but  no  one  of  them  is  energy;  and  energy 
is  not  known  in  experience  when  disembodied,  that  is,  outside 
of  some  substantial  thing,  and  then  only  shows  itself  in  the 
degree  and  kind  of  activity  of  that  thing.  It  is  in  all  of  our 
experiences  an  exchangeable  commodity,  but  there  is  never  an 
exchange  except  a  mass  of  matter  of  some  degree  of  magnitude 


HO IV  PHENOMENA    ARE   INTERPRETED.  75 

is  present,  and  conditions  the  exchange  either  in  character  or 
amount.  There  is  no  physical  thing  which  possesses  it  and  is 
able  to  impart  any  of  it  to  another  thing  without  an  equal  loss 
to  itself.  Yet  the  above  conception  of  something  with  inher- 
ent energy,  able  to  move  other  bodies  in  this  way  or  that,  with- 
out being  depleted  in  its  store,  implies  as  much.  To  make  the 
matter  clearer,  suppose  a  mechanical  engine  to  be  thus  endowed 
with  energy  inherent  in  it  and  able  to  act  without  loss  ;  evidently 
it  would  be  what  we  would  call  a  perpetual  motion, — would  give 
power  indefinitely,  and  that  without  any  supply  for  its  expendi- 
ture. It  would  mean  an  infinite  source  in  a  finite  thing,  and  a 
finite  thing  which  can  do  an  infinite  amount  of  work.  If  this 
be  considered  as  an  attribute  of  mind,  that  is,  such  a  mind  as 
humanity  exhibits  and  which  each  individual  of  us  is  assumed 
to  possess,  then  each  one  of  us  would  so  far  be  independent  of 
antecedents,  and  would  need  no  other  resources,  which  is  con- 
trary to  our  uniform  experiences.  It  should  be  noted  that  this 
cannot  be  considered  as  a  matter  of  degree,  that  is,  ability 
to  do  more  or  less,  for  the  smallest  thing  or  object  possessing 
ability  to  do  work  of  any  kind  without  a  physical  supply  from 
some  other  source  can  do  an  infinite  amount  of  work  in  an 
infinite  time.  The  whole  has  to  be  granted  or  nothing.  If  we 
are  to  eschew  romancing  and  interpret  phenomena  in  accordance 
with  our  uniform  experiences,  that  is,  scientifically,  —  for  that  is 
scientific  method, —  then  it  seems  plain  that  one  must  surrender 
the  notion  that  life  and  mind  energize  ordinary  matter  which  is 
otherwise  inert  or  dead.  There  is  something  wrong  in  one 
assumption  or  the  other  as  to  the  nature  of  mind  or  the  nature 
of  matter  or  possibly  both. 

What  reason  has  been  given  or  can  be  given  for  supposing 
that  matter,  as  we  know  it,  is  inert  and  incapable  of  doing  any- 
thing }  There  are  two  answers  to  this,  one  coming  from  relig- 
ious or  theological  sources,  the  other  from  a  physical  source ; 
the  former  probably  derived  from  the  story  of  the  creation  of 
living  things  wherein  special  creative  acts  were  needed  to  endow 
matter  with  life,  and  a  second  creative  effort  to  endow  a  living 
thing,  man,  with  a  soul.  Such  a  view  assumed  that  matter 
had  in  it  neither  life  nor  mind,  and  therefore  considered  it  as 


76  BIOLOGICAL   LECTURES. 

both  inert  and  inanimate.  Each  particle  was  imagined  to  be  a 
minute  something  created  out  of  nothing.  Its  properties  were 
not  inherent  in  it,  but  were  imposed  upon  it,  and  might  have 
been  different  if  the  deity  had  so  willed.  Of  the  latter  it  is  to 
be  said  at  the  outset  that  physical  philosophers  have  almost 
always  accepted  their  first  principles  from  theologians  and  have 
aimed  to  the  best  of  their  ability  to  interpret  phenomena  in 
accordance  with  such  assumptions.  It  was  so  in  astronomy, 
in  geology,  in  physiology,  in  biology.  Because  no  one  ever 
saw  a  stone  or  other  so-called  inanimate  object  roll  up  hill,  or 
do  something  which  an  animal  might  do,  it  was  thought  to  be 
unable  to  do  anything,  whereas  every  one  knows  and  always 
has  known  that  it  would  roll  down  hill  without  any  agency 
different  from  its  own  ;  also  that  one  of  the  laws  of  motion 
affirms  that  action  and  reaction  are  equal,  and  if  one  kicks  such 
a  stone,  it  will  kick  back  in  return.  Experience  of  each  one  of 
us  teaches  the  temerity  of  the  action.  A  lump  of  coal  and  a 
loaf  of  bread  might  lie  in  one  place  indefinitely  long  ;  but  would 
that  imply  they  were  inert  things  and  without  energy  or  ability 
to  do  anything.!*  No;  it  would  only  imply  that  whatever  energy 
they  might  have  would  not  show  itself  by  a  change  of  position 
of  the  whole  body.  The  loaf  of  bread  is  made  up  of  particles 
of  carbon,  hydrogen  and  oxygen  with  a  trace  of  phosphorus, 
sulphur,  lime,  and  three  or  four  other  elements  in  less  quantity 
still.  If  eaten  by  an  animal  it  will  furnish  it  with  energy  for 
doing  various  kinds  of  work.  If  fed  to  a  steam  engine  in  a  like 
manner  it  will  raise  weights  or  propel  itself.  If  it  furnisJies 
energy  it  must  be  because  it  has  energy  ;  and  if  it  has  energy 
it  is  not  inert.  In  a  like  manner  the  lump  of  coal  has  energy, 
for,  if  fed  to  a  steam  engine,  it  enables  the  latter  to  do  its  work. 
If  the  lump  weighs  a  pound  it  is  capable  of  doing  ten  millions 
of  foot  pounds  of  work,  which,  if  applied  to  itself,  would  raise  it 
two  thousand  miles  high.  Can  a  body  which  possesses  such  an 
amount  of  energy  as  that  in  any  form  be  called  an  inert  body  .-* 
The  trouble  in  thinking  of  such  phenomena  is  here.  Evidences 
of  energy  have  been  looked  for  only  in  the  ability  of  a  body  to 
do  a  certain  thing,  namely,  change  its  position.  Let  a  man  be 
sleeping  soundly  and  he  does  not  change  his  position.     If  he  is 


HOW  PHENOMENA    ARE   INTERPRETED.  "JJ 

to  be  moved,  others  have  to  do  it,  but  no  one  would  think  of 
calling  a  sleeping  man  inert.  For  the  time  being  he  is  unable 
to  use  his  energy  in  that  particular  way,  and  energy  may  exist 
in  many  different  ways.  The  smallest  particle  of  coal  we  can 
see  in  a  microscope  possesses  its  proportional  part  of  energy  of 
that  kind,  and  one  must  perforce  assume  the  same  things  true 
of  the  atoms  of  carbon  ;  but  that  is  the  same  thing  as  saying  that 
carbon  atoms  are  not  inert  things,  and  the  same  thing  is  to  be 
said  of  oxygen,  hydrogen,  and  the  rest.  And  there  is  no  evi- 
dence that  any  kind  of  a  physical  process  could  ever  extract  all 
its  energy,  for  there  is  the  best  of  physical  evidence  that  atoms 
of  all  sorts  are  not  only  indestructible  by  physical  processes, 
but  that  they  possess  inherent  energy,  and  are  also  able  to 
absorb  other  energy  to  a  perfectly  unlimited  extent  from  the 
medium  in  which  they  exist,  namely,  the  ether ;  also  that  they 
react  upon  the  ether  because  of  their  own  inherent  energy. 
Observe  in  all  this  that  I  am  talking  about  matter  in  its  atomic 
forms,  not  as  foreign  bodies  acted  upon  by  this  or  that  kind  of 
energy,  but  as  being  themselves  the  very  embodiment  of  energy 
and  reacting  in  every  case  in  accordance  with  the  law  of 
energy. 

Physical  philosophers  had  sufficient  data  for  all  this  long  ago, 
but  their  philosophical  preconceptions  prevented  its  significance 
from  being  seen  until  Joule,  Faraday,  Helmholtz,  and  a  few 
others  developed  what  is  called  the  doctrine  of  the  Conser- 
vation of  Energy.  Even  with  all  the  evidence  we  have  to-day, 
there  are  many  physicists  and  chemists  who  follow  afar  off. 
Some  are  afraid  from  religious  convictions,  others  are  not 
interested  in  fundamental  questions  at  all,  and  so  pay  no  at- 
tention to  them  ;  still  others  are  muddled  with  terminology, 
which  is  frequently  misleading,  and  such  try  to  convince  them- 
selves and  others  that  not  so  much  is  known  as  is  known. 
The  outlook  is  not  such  as  they  expected,  and  the  interpreta- 
tion is  so  far  from  their  hazy  ideals  that  the  new  knowledge 
and  all  its  implications  are  repudiated  without  being  appre- 
hended. If  matter  and  its  relations  are  not  what  they  have 
been  believed  to  be,  and  if  the  growth  of  knowledge  has  been 
steadily  away  from  the  older  conceptions,  so  that  not  a  single 


yS  BIOLOGICAL   LECTURES. 

one  of  them  has  been  verified  in  physical  science,  there  is  left 
the  strong  presumption  that  the  remainder  will  turn  out  to  be 
as  far  from  the  truth  as  have  those  which  are  already  settled, 
if,  peradventure,  anything  can  be  said  to  be  settled. 

Perhaps  most  persons  who  are  satisfied  with  the  modern 
doctrine  of  phenomenal  relations  and  are  willing  to  concede 
that  our  notions  of  the  constitution  and  nature  of  matter 
needed  revision,  and  who  do  not  object  on  any  ground  to  the 
physical  interpretations  and  explanations,  may  feel  and  say : 
"  Granted  all  you  say  about  the  whole  of  physical  science,  that 
matter  itself  is  not  what  it  was  thought  to  be  or  to  be  like,  even 
to  the  extent  of  being  alive  in  some  measure,  it  would  not  fol- 
low that  matter  as  such  could  feel  or  think  or  know,  and  this 
is  what  the  whole  contention  is  and  has  been  about,  not  whether 
the  physical  constitution  of  things  is  thus  or  thus.  There  is 
no  evidence  that  matter  as  such  is  intelligent."  This  is  a  judg- 
ment as  to  the  nature  and  possibilities  of  matter  based  on  some 
a  p}iori  philosophy,  not  upon  a  study  of  the  thing  itself.  Who 
are  they  who  make  such  an  assertion  }  Those  who  know  most 
about  matter  and  its  possibilities  .<*  Any  one  who  could  stand 
an  examination  upon  the  subject  for  five  minutes.-*  I  think  not. 
Such  may  have  feeling  but  not  knowledge  for  this  belief.  If 
one  is  to  explain  phenomena  on  the  basis  of  what  is  known,  if 
all  kinds  of  phenomena  are  necessarily  interrelated,  then  it  is 
proper  to  ask  if  there  be  any  evidence  that  such  activities  as 
feeling,  knowing,  thinking,  exist  apart  from  material  structure  t 
As  a  matter  of  fact  is  it  not  entirely  true  that  wherever  there 
is  evidence  for  either  there  is  abundant  evidence  for  material 
structure.'*  If  such  matter  be  inert,  as  has  been  so  long  assumed, 
then  it  was  a  fair  inference  that  something  other  than  its  own 
resources  must  be  summoned  in  order  to  account  for  any  kind 
of  a  happening.  If,  on  the  other  hand,  matter  be  not  inert  but 
endowed  with  energy,  then  what  matter  can  do  and  what  may  be 
expected  of  it  need  further  looking  into,  as  is  indeed  the  case. 

If  what  I  have  presented  has  any  proper  warrant  in  fact,  there 
is  then  a  warning  to  be  heeded  against  assuming  on  limited 
knowledge  what  are  the  possible  properties  of  matter  and  assert- 
ing what  it  cannot  do.     The  difficulty  of  forming  any  concep- 


HOIV  PHENOMENA    ARE  INTERPRETED.  79 

tion  of  how  such  unlike  phenomena  as  feeling  and  material 
movements  can  be  related  is  great,  but  we  have  plenty  of  evi- 
dence that  we  have  grown  into  conceptions  which  are  apparently 
as  unlikely  as  these.  For  instance,  what  possible  relations 
can  there  be  between  turning  a  crank  and  that  which  is 
called  electricity,  which  travels  in  a  wire  or  in  an  empty 
space  with  the  velocity  of  186,000  miles  a  second,  glows  like 
the  sun  in  an  arc  lamp,  and  will  serve  for  a  chat  with  a 
friend  in  Chicago  as  if  you  were  face  to  face.  Yet  there 
is  now  known  to  be  a  direct  and  quantitative  relation,  and  the 
explanation  of  the  whole  thing  lies  in  the  properties  of  the 
atoms  themselves  —  properties  which  were  unimagined  not 
a  long  time  ago.  So  as  knowledge  has  advanced  the  whole 
drift  of  it  has  been  to  enlarge  the  possibilities  of  matter  itself, 
and  this  reflection  serves  to  make  it  more  and  more  probable 
that  all  the  other  phenomena  exhibited  by  matter  are  due  to  its 
inherent  qualities.  We  must  wholly  discard  the  old  view  of  it 
and  adopt  a  larger  view.  One  must  ask  again  what  is  the  pos- 
sible nature  of  matter,  and  can  any  one  tell  enough  about  it  to 
help  on  a  step  in  the  process,  —  especially  to  bridge  such  a 
chasm  as  appears  between  mind  and  matter } 

We  do  have  a  new  conception  of  matter  which  is  now  so  well 
vouched  for  that  both  the  physicists  and  chemists  are  inter- 
preting phenomena  by  its  means.  This  is  that  the  atoms  of 
matter  are  vortex  rings  in  the  ether  and  made  of  ether  itself  ; 
they  are  simply  whorls  of  ether  and  are  not  something  else 
created  in  ether,  and  all  the  properties  it  manifests  are  due  not 
more  to  the  structure  than  to  the  stuff  it  is  made  of ;  and  if  this 
be  the  fact,  the  whole  controversy  concerning  matter  and  its 
properties  and  possibilities  becomes  a  controversy  about  some- 
thing else  than  matter,  namely,  the  ether.  It  is  discovered  that 
the  characteristics  of  matter  do  not  belong  to  the  ether,  and 
that  nearly,  if  not  all  terms  we  use  to  describe  matter  phenom- 
ena are  wholly  inapplicable  to  the  ether ;  indeed,  we  are  without 
proper  terms  to  describe  them.  Matter  as  we  know  it  is  made 
up  of  particles  ;  ether  is  not.  Matter  is  more  or  less  porous  ;  the 
ether  is  without  interstices, — it  is  called  a  continuous  medium 
and  is  boundless  in  extent.     Matter  is  subject  to  friction,  and 


8o  BIOLOGICAL   LECTURES. 

all  mechanical  movements  of  it  are  soon  brought  to  rest.  The 
ether  is  frictionless.  Matter  has  gravity  ;  the  ether  is  without 
it.  Hence  it  is  plain  that  one  must  not  include  ether  when  he 
is  talking  about  matter,  for  it  is  altogether  a  different  some- 
thing with  different  and  unknown  and  undiscovered  qualities, 
and  no  one  has  been  able  to  deduce  the  properties  of  matter, 
as  we  know  it,  from  the  properties  of  ether.  It  is  plainly  the 
agency  by  which  light  and  heat  get  to  us  from  the  sun  and  stars, 
by  which  electric  and  magnetic  phenomena  become  apparent. 
Gravity  is  chargeable  to  its  pressure  instead  of  to  the  attraction 
of  matter.  It  transmits  wave  motions  at  the  rate  of  186,000 
miles  a  second,  but  it  transmits  gravity  more  than  200,000  million 
miles  a  second.  Some  of  the  phenomena  it  exhibits  seem  to 
show  it  to  be  an  enormous  storehouse  of  energy,  —  one  million 
horse  power  per  cubic  foot  is  a  low  estimate  for  it.  Like  astro- 
nomical distances  and  magnitudes  it  may  be  computed  but  not 
conceived.  With  all  this  it  is  entirely  incapable  of  affecting 
any  of  our  senses.  We  are  without  any  nerves  capable  of  per- 
ceiving it,  and  belief  in  the  existence  of  such  a  medium  has 
been  forced  upon  men  of  science  because,  first,  every  former 
supposition  has  experimentally  broken  down  ;  second,  because, 
as  Sir  Isaac  Newton  said,  it  is  impossible  to  think  that  one 
body  can  act  upon  another  not  in  contact  with  it  without  some 
kind  of  a  medium  between  them  ;  and  lastly,  because  energy  does 
get  from  one  body  to  another  in  the  absence  of  ordinary  matter, 
as  is  exhibited  by  the  heat  and  light  of  the  sun,  and  the  rate  of 
transference  can  be  measured  in  several  ways.  The  interpre- 
tation of  the  physical  facts  observed  has  necessitated  it,  and  by 
its  means  otherwise  inexplicable  diflficulties  are  overcome.  I 
think  there  is  not  a  physicist  of  any  nation  or  rank  who  has 
attended  to  the  facts,  who  is  not  satisfied  of  the  existence  of 
what  we  call  ether,  but  no  one  can  describe  it  or  tell  how  it  can 
and  how  it  does  act  upon  matter.  We  are  in  almost  total  igno- 
rance about  it.  If  it  is  hazardous  to  set  limits  to  the  possibilities 
of  matter  with  the  advantage  of  what  knowledge  we  have  of  it, 
what  shall  be  said  of  the  attempt  to  limit  the  qualities  and 
possibilities  of  what  we  know  nothing  about,  —  ether!  The 
mystery  of  matter  is  great,  but  is  nothing  to  the  apparent  mys- 


NOPV  PHENOMENA    ARE   INTERPRETED.  8 1 

tery  of  the  ether  ;  and  if  matter  be,  as  I  have  hinted,  a  particular 
form  of  energy  in  the  ether,  then  what  can  happen  in  matter 
depends  upon  the  wholly  unknown  possibilities  of  the  ether. 
Again,  if  the  phenomena  exhibited  by  matter  lead  to  the  con- 
viction that  the  latter  is  made  up  of  the  fornjer,  then  logic  leads 
to  the  necessary  assumption  that  the  ether  must  have  existed 
before  matter,  which  is  made  out  of  it,  and  so  far  such  a  con- 
clusion finds  favor  with  all  philosophers.  In  physical  philoso- 
phy a  phenomenon  is  said  to  be  explained  or  interpreted  when 
its  antecedents  are  all  pointed  out.  When  such  antecedents 
are  unknown  we  strive  to  discover  the  missing  factor,  always 
assuming  that  whatever  it  may  be  it  has  some  necessary  relation 
to  the  phenomenon  which,  when  discovered,  may  be  made 
intelligible  in  the  same  terms  the  rest  have  been.  Note  how 
this  applies  to  the  explanation  of  the  existence  of  matter  itself. 
A  uniform,  homogeneous,  frictionless,  gravitationless  medium, 
such  as  the  ether  appears  to  be,  could  not  itself  organize  a 
single  vortex  ring  possessing  energy,  which  should  be  the  in- 
destructible thing  an  atom  appears  tQ  be.  Mechanical  actions 
such  as  belong  to  our  scientific  scheme  of  knowledge  are  abso- 
lutely powerless  in  a  frictionless  medium,  and  in  order  to  pro- 
duce such  a  thing  as  an  atom  there  is  needed  an  activity 
altogether  unrelated  to  any  kind  we  know  or  which  has  ever 
been  the  subject  of  consideration  in  physical  science.  Creation 
is  the  only  word  which  is  suitable  for  the  action,  and  there  is 
implied  behind  the  ether  some  other  factor  not  necessarily  related 
to  it  in  the  sense  in  which  ether  is  related  to  matter.  So  that 
behind  both  matter  and  ether  there  is  a  something  which  must 
be  postulated  as  the  initiative  of  all  we  see  and  know,  capable 
of  acting  upon  the  ether,  but  without  mechanical  compulsion. 
Therefore  choice,  a  mental  attribute,  has  a  locus  here,  and  mind 
appears  to  be  a  necessary  assumption,  as  necessary  for  a  proper 
antecedent  as  is  ether  pressure  for  the  phenomena  of  attraction 
or  an  artificer  for  making  a  house,  and  this,  too,  wherever  there 
is  an  atom,  whether  here  upon  the  earth  or  in  the  most  distant 
star, — everywhere,  omnipresent  mind.  Choice  implies  con- 
sciousness and  intelligence,  and  so  physical  interpretations  of 
the  phenomena  always  before  our  eyes  lead  us  back  to  a  super- 


82  BIOLOGICAL   LECTURES. 

physical  beginning.  If  we  find  energy  in  the  form  of  matter, 
it  is  not  necessarily  there.  If  we  find  life  in  it,  it  is  because 
mind  is  operative  in  all  ether  and  therefore  in  all  matter,  and 
cannot  be  exorcised  from  it.  Some  philosophers  speak  of  this 
as  **  infinite  and  eternal  energy,"  but  it  is  not  such  energy  as 
the  physicist  measures  in  foot  pounds.  Other  philosophers 
call  it  God,  and  can  one  express  in  terser,  truer  or  more 
scientific  language  the  relation  of  mankind  to  this  infinite  power 
than  did  Paul  in  Athens  :  "  In  Him  we  live  and  move  and  have 
our  being." 


SIXTH     LECTURE. 


KNOWN    RELATIONS    BETWEEN    MIND   AND 
MATTER. 

A.    E.    DOLBEAR. 

We  have  a  body  of  knowledge  which  we  call  science.  In  a 
few  —  a  very  few  —  instances  it  is  so  far  perfected  we  can  use 
it  for  prevision,  and  thus  we  make  almanacs,  learn  when  the 
moon  will  be  eclipsed,  and  when  the  tide  will  come  in,  how  to 
make  a  steam-engine  or  a  dynamo  to  do  a  specific  amount  of 
work,  and  so  on ;  but  for  nearly  every  question  in  which 
humanity,  as  a  whole,  has  an  immediate  interest  there  is  now 
no  satisfactory  answer,  which,  broadly  stated,  means  that  there 
is  yet  no  science  which  can  be  applied  to  them  in  the  same 
sense  as  it  can  be  applied  to  astronomical  problems.  The  best 
one  can  do  is  to  hold  any  opinion  very  gently,  and  be  ready  to 
abandon  it  at  once  if  occasion  comes. 

"The  science  of  life,"  — that  is  what  we  all  want  to  under- 
stand in  order  to  get  the  most  out  of  it.  That  there  is  a 
possible  science  of  life  everybody  believes.  In  every  great 
emergency  among  men  there  are  always  a  number  of  persons 
who  are  ready  to  tell  us  about  it,  and  what  should  be  done  to 
avoid  catastrophe.  When  Jerusalem  was  in  a  state  of  siege 
there  were  several  who  claimed  to  be  the  Messiah,  each  promis- 
ing deliverance  if  the  people  would  but  hearken  to  them ;  but 
in  the  multitude  of  such  Messiahs,  how  could  one  judge  which 
was  the  true  one  except  he  should  actually  deliver  them  from 
their  troubles,  whether  they  believed  in  him  or  not  ?  The  test 
for  one's  ability  is  what  he  does,  not  what  he  promises  to  do. 
So  there  are  teachers  and  preachers  and  makers  of  books  who 
tell  how  it  is,  and  what  to  do,  yet  we  are  no  wiser,  and  society 


84  BIOLOGICAL   LECTURES. 

is  troubled  with  trusts,  monopolies,  strikes,  theories  of  taxa- 
tion, of  protection,  of  values,  of  liberty,  of  free-will,  of  the 
family,  of  education,  of  heredity,  of  life  itself ;  and  who  shall 
deliver  us  ?  To  say  that  science  will  may  be  true  enough,  but 
she  cannot  to-day. 

In  his  Locksley  Hall  Tennyson  wrote  more  than  fifty  years 

ago:  — 

"  Science  moves  but  slowly,  slowly, 
Creeping  on  from  point  to  point." 

And  that  was  true  then,  and  in  large  measure  is  true  to-day, 
concerning  all  those  matters  that  relate  more  nearly  to  us  in 
our  everyday  lives.  When  we  laud  science,  and  tell  how 
much  has  been  accomplished  within  the  past  fifty  years,  it  is 
just  as  well  to  remember  that  what  has  been  achieved  in  this 
domain  has  been  mostly  in  the  purely  mechanical  field.  We 
feel  quite  sure  we  now  know  how  the  Solar  system  came  to  be 
as  it  is,  —  through  a  series  of  slow  changes  by  which  a  huge 
molecular  cloud  of  dust  in  space  becomes  a  body  of  rotating 
globes  revolving  about  a  central  hot  mass.  We  feel  quite 
confident  that  what  we  call  the  doctrine  of  energy  is  true,  and 
that  it  is  not  created  or  annihilated  by  any  processes  in  our 
experience.  We  are  almost,  if  not  quite  convinced  that  the 
animals  and  plants  upon  the  earth  to-day  are  the  descendants 
in  unbroken  line  from  the  simplest  microscopic  forms  of  living 
things  in  the  far  off  geologic  ages,  and  we  put  all  these  things 
together  and  call  the  process  of  becoming  something  different, 
—  evolution ;  and  for  convenience  we  call  some  mechanical 
science,  and  some  molecular  science,  and  some  biologic  science, 
according  as  the  subject-matter  is  among  big  bodies  or  little 
bodies  or  living  bodies.  But  it  is  sometimes  forgotten  or 
overlooked  that  the  same  forces  are  at  work  with  the  little  as 
with  the  big  bodies,  and  that  no  body,  large  or  small,  can  be 
separated  from  the  action  of  all  the  rest,  and  that  no  particle 
of  matter  ever  lets  go  its  grip  on  any  other  one.  These  things, 
I  have  said,  we  think  we  know ;  but  may  I  not  say  we  do  know, 
if  we  really  do  know  anything.?  If  there  be  any  doubt  about 
gravitation,  about  the  laws  of  energy,  about  the  multiplication 
table,  then  one  may  harbor  doubts  about  any  thing  he  pleases  ; 


RELATIONS  BETWEEN  MIND   AND   MATTER.        85 

and  there  is  justification  for  even  this  doubt.  Have  not  the 
mathematicians  lately  told  us  emphatically  that  there  are  no 
axioms,  that  all  once  held  as  absolutely  true  about  lines  and 
angles  —  in  short,  geometry  —  has  no  better  basis  than  experi- 
ment and  the  narrow  limits  of  our  experience,  thus  bringing  our 
rational  powers  to  a  standstill  in  the  presence  of  problems  out 
of  the  range  of  our  instruments  ?  This  is  precisely  what  has 
been  done,  and  for  all  we  know  the  universe  may  be  a  very 
different  thing  from  what  it  has  seemed  to  be,  for  in  concluding 
what  it  is  we  have  always  assumed  that  space  was  what  it 
seemed  to  be,  and  that  ideally  one  could  go  in  a  straight  line 
on  and  on  forever.  Now  we  do  not  know  that,  say  the  mathe- 
maticians ;  and  they  talk  of  space  of  four  or  more  dimensions 
where  our  laws  of  physics  and  energy  will  not  hold.  And 
more  than  that,  some  of  them  begin  to  derive  comfort  from 
the  reflection  that,  after  all,  the  universe  is  not  half  so  simple 
and  easy  to  understand  as  they  had  once  thought,  and  that  the 
possibilities  of  knowledge  and  of  existence  may  vastly  exceed 
"  anything  any  one  has  yet  imagined.  For  us,  then,  science 
must  be  correlated  experiences^  and  for  us  the  truth  can  only  be 
that  statement  which  is  in  accordance  with  the  best  and  most 
certain  other  things  we  know  ;  it  must  be  in  accordance  with 
our  geometry,  our  energy,  with  our  modes  of  thought,  and  then 
always  with  the  reservation  that  what  to-day  seems  funda- 
mental may  ultimately  turn  out  to  be  derived,  and  relations 
that  seem  obvious  may  be  far  from  it. 

All  this  is  a  sort  of  disclaimer  against  being  taken  for 
one  who  believes  and  teaches  that  the  knowledge  we  have 
is  sufficient  to  enable  him  or  others  to  deduce  all  phenom- 
ena, or  even  to  foresee  in  any  kind  of  way  how  to  answer 
properly  many  of  the  questions  which  concern  us  all.  The 
decalogue  was  mostly  a  compendium  of  dotitSy  and  the  best 
that  such  science  as  I  have  knowledge  of  can  now  do  is 
to  tell  us  what  not  to  do,  rather  than  what  at  once  to  do, 
and  gives  a  mere  hint  as  to  the  direction  one  must  look  for 
further  light  on  any  or  all  of  them.  Of  course  we  all  know 
how  men  have  speculated  on  both  mind  and  body  and  their 
relation,  and  it  has  always  been  quite  the  fashion  to  go  into 


86  BIOLOGICAL   LECTURES. 

the  history  of  the  steps  in  thought  from  the  earliest  time  till 
now  when  treating  on  this  and  kindred  topics, — a  course 
which  implies  there  has  been  some  kind  of  progress,  and 
that  each  generation  has  contributed  in  some  degree  to  the 
solution.  It  hardly  needs  to  be  said  that  this  is  no  more  true 
in  this  matter  than  in  any  other  of  the  sciences.  In  astronomy 
one 'need  not  go  back  of  Copernicus.  In  chemistry  one  need 
not  go  back  of  Dalton.  In  electricity  one  need  not  go  back  of 
Franklin  ;  in  heat,  back  of  Sir  Humphrey  Davy ;  in  biology, 
back  of  Darwin.  Not  that  there  was  nothing  known  before 
them,  but  what  was  known  was  of  little  and  no  importance. 
If  all  biologic  knowledge  before  1840  were  subtracted  from 
present  knowledge,  it  would  scarcely  be  missed  ;  and  if  in  these 
fundamental  things  there  was  nothing  of  importance,  still  more 
true  is  it  in  the  more  difficult  and  unexplored  field  of  mind  and 
its  bodily  relations.  There  is  not  a  single  philosopher  from 
Adam,  and  the  year  i  up  to  1850,  whose  knowledge  and 
opinions  on  the  question  are  worth  a  hearing  ;  and  all  refer- 
ences to  the  expressed  or  implied  statements  of  any  of  them, 
as  having  any  weight  at  all  in  the  settlement  of  any  of  these 
questions,  seem  to  me  to  be  utterly  useless, — as  useless  as 
their  speculations  on  the  habitability  of  the  planets.  None  of 
them  had  adequate  data ;  in  fact,  they  knew  nothing  about  it. 
If,  also,  one  remembers  that  modern  knowledge  is  not  ancient 
or  mediaeval  knowledge  confirmed  and  expanded,  but  new 
knowledge  which  contradicts  and  repudiates  most  of  the  old, 
he  will  see  still  less  reason  for  appealing  to  antiquity  for  the 
support  of  any  doctrine.  Now,  seeing  that  the  theologians 
have  admitted  that  the  Bible  was  given  for  instruction  in 
religious  things,  not  in  science,  it  is  no  longer  safe  to  quote 
scripture  as  a  warrant  for  any  opinion  upon  a  question  involv- 
ing scientific  data  or  method  ;  hence,  even  on  the  question  of 
mind  and  body  no  one  looks  there  either  for  direction  or 
corroboration. 

By  body  we  mean  the  matter  which  constitutes  the  animal 
mechanism,  as  that  which  embodies  the  various  functions  of 
growth,  assimilation,  movements  of  one  kind  and  another,  and 
along  with  these  exhibits,  in  some  degree  some  order  of  intelli- 


RELATIONS   BETWEEN  MIND   AND   MATTER.        ^J 

gence.  Once  there  seemed  to  be  sufficient  reason  for  dividing  liv- 
ing things  into  plants  and  animals.  That  was  when  knowledge 
was  fragmentary ;  but  now  there  is  no  line  between  them, 
and  no  naturalist  can  so  define  one  as  to  exclude  the  other. 
The  possession  of  what  is  called  irritability,  by  which  is  meant 
ability  to  respond  by  movement  of  some  kind  to  an  external 
stimulus,  is  no  longer  a  peculiar  characteristic  of  what  have 
been  called  animals,  for  there  are  many  plants  that  possess  it 
in  a  marked  degree ;  and  there  are  free  swimming  plants,  such 
as  bacteria.  Experimental  research  with  the  microscope  has 
shown  that  this  quality  exists  in  all  plants  in  some  degree,  and 
that  in  all  cases  the  reaction,  of  whatever  kind  it  may  be,  shows 
evidence  of  what,  in  higher  forms  of  living  things,  is  always 
attributed  to  intelligence;  that  is,  the  reaction  is  adaptive. 
This  does  not  mean  what  in  higher  living  things  we  call  choice, 
but  it  does  mean  that  the  energy  resident  in  the  organism 
works  spasmodically,  automatically,  and  mechanically  in  a  very 
wonderful  manner,  and  gives  rise  to  phenomena  which  have 
been  thought  could  only  appear  where  there  was  some  kind  of 
animal  existence  as  distinct  from  a  vegetable.  The  discovery 
of  sensitivity  as  a  quality  belonging  to  all  plants  is  new,  and 
makes  it  still  more  important  that  one  should  inquire  further 
as  to  whether  other  distinctions  are  as  real  as  they  have  been 
thought  to  be.  Once  a  vital  force  was  believed  to  be  resident 
in  living  things,  and  this  force  was  supposed  to  control  diges- 
tion, nutrition,  growth,  and  feeling,"  but  all  biologists  have 
discarded  the  idea.  I  do  not  know  of  a  single  naturalist  of 
any  distinction  in  the  world  who  does  not  think  and  say  that 
all  the  phenomena  exhibited  by  plants  and  animals  are  due  to 
physical  and  chemical  causes  alone.  In  a  late  lecture  Professor 
Stokvis,  of  Amsterdam  University,  said  :  "  Certain  it  is  that 
life  is  a  chemical  function,"  and  he  thinks  it  is  proved  beyond 
a  peradventure.  To  present  the  evidence  for  it  would  be  to 
make  a  book ;  and  seeing  that  it  is  so  generally  accepted  in 
scientific  quarters,  where  it  would  first  meet  opposition  if  it 
could  be  opposed,  one  may  accept  it,  —  at  any  rate,  provisionally. 
But  what  is  meant  by  life }  Well,  in  brief,  it  means  the 
sum    of   the  activities   possessed   by   living  things,   including 


88  BIOLOGICAL   LECTURES. 

growth,  assimilation,  reproduction.  If  such  qualities  are  really 
only  refined  physics  and  chemistry,  as  has  been  stated,  then  is 
it  much  matter  for  wonder  that  our  predecessors  did  not  find 
it  out,  seeing  that  they  had  no  knowledge  of  either  ?  Now,  the 
outcome  of  what  is  called  life,  even  in  the  lowest  and  so-called 
insensate  forms,  is  wonderful  enough,  and  is  so  different  from 
what  has  been  supposed  to  be  possible  to  mere  matter,  that  it 
is  worth  the  while  to  stop  and  consider  why  it  has  seemed  so 
different. 

The  philosophers  in  all  the  past  have  had  a  kind  of  theory 
of  things  to  maintain,  as  to  how  man  came  to  be  on  the  earth, 
and  especially  how  evil  came  to  be  his  portion.  Man  was 
created  upright  and  good,  but  by  transgression  he  fell,  and  the 
earth  with  him  was  cursed.  This  theory  required  the  concep- 
tion of  the  matter  or  material  of  which  the  earth  is  made  as 
being  utterly  inert  and  dead.  The  idea  was  that  life,  as  we 
know  it,  was  breathed  into  it,  and  not  until  then  was  there  any 
living  thing.  Matter  was  not  only  lifeless,  but  it  was  gross, 
and  all  sorts  of  epithets  were  applied  to  it  to  make  wider  the 
distinction  between  it  and  a  living  thing.  From  a  dictum  it 
became  a  belief  ;  and,  although  there  was  no  one  who  could 
prove  it,  or  took  any  steps  to  prove  it,  it  came  to  be  considered 
true,  and  the  proposition  that  matter  had  no  power  to  do  any- 
thing by  itself  was  thought  to  be  almost  axiomatic,  and  that  in 
spite  of  the  wonderful  succession  of  all  kinds  of  phenomena 
witnessed  every  day,  —  combustion,  the  falling  of  an  apple, 
the  formation  of  clouds  and  dew  and  hail,  the  recurrence  of 
day  and  night,  the  explosion  of  powder,  of  gas,  and  others  just 
as  well  known,  all  showing  that  matter,  so-called  inorganic 
matter,  did  in  some  way  possess  active  properties  of  certain 
kinds  by  which  it  could  change  phenomena  solely  through  its 
own  powers.  It  is  endowed  with  energy.  Mix  sulphur,  carbon 
and  saltpetre  together  —  the  mixture  you  call  powder;  but  you 
are  aware  that  the  compound  possesses  tremendous  energy 
which  you  have  not  imparted  to  it  ;  and  so  does  all  matter  — 
every  atom  of  it  —  possess  energy  of  a  kind  that  enables  it, 
under  proper  conditions,  to  do  the  most  wonderful  things  ;  and 
yet  this  was  not  suspected  for  thousands  of  years,  and  even 


.     RELATIONS  BETWEEN  MIND   AND   MATTER.        89 

after  it  was  discovered  it  was  not  perceived  for  a  long  time 
that  the  inertness  of  matter  could  no  longer  be  held  as  a  tenet 
in  philosophy.  There  are  plenty  of  teachers  yet  who  think 
matter  to  be  inert,  and  as  possessing  no  energy.  But  what  is 
energy }  Simply  the  ability  of  a  body  to  act  on  other  bodies 
so  as  to  move  them  in  one  way  or  another. 

That  kind  of  action  which  is  called  chemical  action,  by  which 
atoms  combine  together  in  certain  definite  ways,  in  which 
atoms  choose  their  partners  and  become  wedded,  is  a  manifes- 
tation of  the  energy  of  atoms,  which  is  ever  present  with  them, 
a  part  of  their  endowment  and  inalienable.  Heat,  light,  elec- 
tricity are  modes  of  the  energetic  action  of  the  ultimate  parti- 
cles of  matter  called  the  elements.  In  all  the  manifestations  of 
these  so-called  forms  of  motion  or  energy,  which  we  employ  for 
economic  uses,  it  ought  not  to  be  forgotten  that  we  do  not 
endow  the  matter,  but  we  find  it  already  endowed,  which  shows 
that  matter  is  not  to  be  considered  as  so  helpless  as  it  has  been 
the  custom  to  think  it  to  be.  But  these  atoms  and  their  com- 
binations—  that  is,  molecules  —  are  often  found  organized  into 
beautiful  forms  called  crystals.  There  are  diamonds  and  sap- 
phires, rubies  and  emeralds,  garnets,  topazes,  beryls,  sugar,  alum, 
and  a  thousand  forms  familiar  enough  everywhere.  These 
symmetrical  forms  are  due  solely  to  the  inherent  qualities  of  the 
substances  themselves,  and  testify  to  the  ability  of  the  matter 
to  arrange  itself,  which  inert  matter  could  not  do.  Dewar  and 
others  have  shown  that  in  the  absence  of  temperature,  chemism 
does  not  exist  ;  and  if  matter  can  do  so  much  as  is  plain  to 
perceive,  is  it  likely  that  these  exhaust  the  possibilities  of  its 
doings  }  We  know  better  already ;  but  I  have  developed  this 
point  far  enough  to  show  what  I  want  to  make  plain,  namely, 
that  matter  has  possibilities  which  the  reigning  philosophy  has 
denied  it  to  have. 

It  has  been  the  custom  to  speak  of  all  the  inherent  qualities 
of  matter  and  the  various  phenomena  which  directly  result  from 
them  as  being  physical  and  chemical.  Are  there  any  such 
purely  physical  and  chemical  phenomena  that  are  really  com- 
parable with  what  we  take  to  be  vital  or  living  phenomena } 
Yes,  a  great  many. 


90  BIOLOGICAL   LECTURES. 

Let  a  crystal,  say  of  quartz,  have  an  end  or  a  corner  knocked 
off.  If  it  now  be  placed  in  a  solution  so  that  growth  can  go  on, 
the  crystal  will  mend  up  its  defacement  so  as  to  be  symmetri- 
cal before  it  will  be  enlarged  elsewhere,  just  as  a  spider  will 
grow  a  new  leg  if  the  old  one  be  removed.  The  cases  are  sim- 
ilar. There  are  so  many  and  so  great  a  variety  of  such  activ- 
ities in  matter  that,  from  the  physical  side,  men  have  been 
forced  to  conclude  that  matter  is  itself  alive,  every  atom  of  it, 
just  as  the  biologists  from  that  side  of  the  study  have  con- 
cluded that  life  is  a  chemical  and  physical  process  simply. 
There  is  agreement  here.  With  such  a  conception  of  matter, 
one  cannot  look  at  any  object  whatever  without  increased 
respect  for  it,  for  not  alone  the  animal  or  insect  which  is  called 
living  possesses  the  distinguishing  vitality,  but  the  very  air  we 
breathe  and  the  dust  under  our  feet.  The  food  we  eat  endows 
us  with  life  because  it  has  it,  not  that  it  creates  it.  We  eat  it 
and  drink  it  and  breathe  it,  and  withal,  life  in  this  view  is  here 
and  always  has  been.  There  is  no  need  for  a  miracle  to  pop- 
ulate the  world,  and  every  star  and  satellite  is  inhabited,  —  yea, 
is  a  living  thing  itself,  the  degree  of  complexity  of  such  life 
depending  solely  upon  the  possible  complexity  of  chemical 
organization.  This  is  an  inference,  of  course,  but  it  follows 
from  the  premises  without  any  circumlocution. 

By  body,  then,  we  mean  a  local  habitat  for  a  living  thing.  We 
also  mean  the  living  thing  itself,  whether  it  be  large  or  small ; 
and  seeing  there  is  no  special  limit  to  the  magnitude  of  a  body 
which  possesses  this  quality,  and  that  there  is  good  reason  for 
holding  that  matter  is  itself  alive,  it  is  apparent  that  it  is  now 
of  importance  to  know  still  more  of  that  thing  we  call  an  atom, 
whether  it  be  of  one  kind  or  another.  We  all  know  what  the 
text-books  say  about  its  properties,  as  of  weight,  hardness, 
density,  elasticity,  impenetrability,  and  so  on.  It  will  be  remem- 
bered, also,  there  are  known  some  seventy  different  kinds  of 
elementary  matter.  If  one  will  stop  an  instant  to  think,  he  will 
see  that  differences  in  size  or  shape  cannot  account  for  such 
differences  in  quality  as  are  presented  by  the  elements.  One 
might  make  of  wood  seventy  different  sizes  and  shapes,  but  the 
density,  hardness,  elasticity,  and  so  on  would  be  the  same  in 


RELATIONS  BETWEEN  MIND   AND   MATTER.        91 

all.  So  there  would  be  needed  as  many  kinds  of  elementary 
stuff  out  of  which  the  atoms  were  made  as  there  were  kinds  of 
atoms,  and  this  complicated  process  and  material  has  no  degree 
of  probability  at  all,  for  the  physical  evidence  we  have  an  abun- 
dance of  to-day  all  goes  to  show  that  nearly,  if  not  quite,  all  the 
physical  qualities  of  the  elementary  atoms  is  due  to  the  quality 
of  their  motions  and  to  nothing  else.  There  is  not  time  to 
enter  upon  this  phase  of  the  question,  but  it  is  true  that  physi- 
cists have  been  led  to  this  conclusion  which  I  quote  from  Karl 
Pearson's  work  on  The  Grammar  of  Science:  "The  whole 
tendency  of  modern  physics  has  been  to  describe  natural  phe- 
nomena by  reducing  them  to  conceptual  motions" ;  also,  "Hard- 
ness, weight,  color,  temperature,  cohesion,  chemical  constitution 
may  all  be  described  by  the  aid  of  the  motions  of  a  single 
medium  which  itself  has  no  hardness,  weight,  color,  tempera- 
ture, nor  indeed  elasticity  of  the  ordinary  type."  If  such  a 
view  of  the  subject-matter  be  true  in  any  sense,  then  one  sees 
at  first  glance  that  what  one  means  by  body  —  that  is,  visible 
masses  made  up  of  this  kind  of  matter  —  must  be  very 
different  from  what  is  involved  in  the  ordinary  conception 
of  it,  and  life  must  be  very  different  in  its  nature  from 
what  it  has  so  long  been  held  to  be.  As  such  matter 
as  is  described  above  cannot  be  created  nor  annihilated 
by  any  physical  or  chemical  process  yet  discovered  or  even 
imagined,  its  very  existence  is  a  guarantee  of  all  of  its  so- 
called  qualities,  even  life  itself,  and  we  come  in  sight  of  a  fact 
of  tremendous  importance  to  every  individual  who  has  tasted 
the  sweets  of  existence  and  who  feels  loth  to  give  them  up, 
especially  when  he  sees  creation  is  so  large,  its  possibilities  of 
gratification  so  boundless,  that  probably  millions  of  years  have 
been  spent  in  leading  up  to  him,  which,  if  he  is  to  cease  con- 
scious existence  at  any  time,  will  apparently  have  been  wasted 
with  little  or  no  profit  to  any.  Some  have  hoped  that  what  is 
called  this  life  is  not  all,  and  they  point  to  this  or  that  as  evi- 
dence for  their  hope,  but  there  has  been  a  total  lack  of  physical 
evidence  for  such  an  issue.  No  one  who  knows  anything  about 
matter  doubts  that  an  atom  of,  say  carbon,  is  practically  an  inde- 
structible thing  ;  that  its  properties  were  the  same  a  million 


92  BIOLOGICAL   LECTURES. 

years  ago  as  they  are  to-day,  and  will  be  the  same  a  million  years 
to  come  ;  and  if  one  knew  it  to  be  a  living  thing  now,  he  would 
expect  it  to  remain  a  living  thing,  and  if  it  were  conscious,  that 
it  would  continue  to  be  conscious.  Another  important  consid- 
eration lies  here.  The  so-called  properties  of  matter  are  not 
detachable  from  matter  itself.  One  cannot  separate  heat  or 
weight  or  vitality  from  a  mass  of  matter ;  they  are  not  entities, 
they  are  qualities.  Set  a  top  spinning  and  how  wonderfully 
it  behaves.  It  will  stand  on  its  point  and  hum,  or  sleep,  as  the 
boys  say;  but  touch  it  ever  so  gently,  and  how  it  will  bound 
away,  and  do  the  most  unexpected  things.  It  is  the  motion  it 
has  which  enables  it  to  act  thus,  and  one  who  did  not  know 
that  the  sleeping  top  was  in  motion,  and  should  notice  what  it 
did  on  being  touched,  might  fairly  well  think  it  had  a  spirit  in 
it.  But  no  one  can  detach  the  spin  from  the  top  so  that  he 
could  hold  the  spin  in  one  hand  and  the  top  in  the  other  ; 
neither  if  life  be  such  a  material  property  can  it  be  detached 
from  what  embodies  it.  If  one  ties  to  physics  at  all  he  must 
not  play  fast  and  loose  with  it.  It  will  not  do  to  take  this  and 
reject  that  because  it  does  not  meet  our  likes  or  wishes.  There 
is  no  evidence  I  am  acquainted  with  that  physics  acts  conjointly 
with  anything  else.  Whatever  it  does,  it  does  on  its  own 
responsibility,  and  the  result  is  to  be  measured  on  its  own 
balance.  This  is  equivalent  to  saying  that  the  field  of  physics 
is  much  broader  than  has  been  supposed.  When  Newton 
lived,  physics  had  to  do  only  with  the  movements  of  large 
bodies.  In  our  time  it  has  been  carried  down  to  atoms,  and,  as 
I  have  said,  the  knowledge  here  gained  has  been  not  simply  an 
extension  of  the  old,  it  has  been  revolutionary  in  its  bearing  on 
all  questions,  and  the  glimpses  it  has  given  of  present  outlying 
fields  convinces  one  that  there  must  soon  come  such  a  hegira 
from  the  old  schools  of  thought  as  has  never  been  witnessed, 
although  the  past  thirty  years  shows  that  in  the  field  of  natural 
history  everybody  has  changed  from  a  creationist  to  an  evolution- 
ist. But  this  has  been  only  the  beginning  of  the  change,  for 
if  that  science  was  true  that  made  such  a  change  necessary,  it 
is  also  true  that  the  same  science  will  make  needful  other 
changes  in  men's  conceptions  of  what  kind  of  a  universe  they 


RELATIONS  BETWEEN  MIND   AND   MATTER.        93 

live  in,  how  it  works,  and  how  they  came  to  be  and  to  think 
as  they  do ;  and  not  unlikely  what  we  please  to  call  evolution 
will  have  to  be  explained  and  restated  in  very  different  terms 
from  those  in  vogue  now. 

So  far  I  have  talked  about  body  and  have  endeavored  to 
show  that  present  science  gives  no  warrant  for  holding  that 
the  matter  which  constitutes  it  is  lifeless  or  inert ;  but,  on  the 
other  hand,  it  does  show  that  it  is  endowed  with  energy,  and 
that  in  enormous  quantity,  and  also  that  the  minute  study  of  it 
has  led  students  from  both  the  biologic  and  physical  side  to 
conclude  that  matter  is  itself  alive,  as  endowed  with  an  inalien- 
able quality,  and  that  the  manifestations  of  this  quality  depend 
upon  the  degree  of  complexity  of  composition  and  arrange- 
ment rather  than  upon  any  superendowment  of  any  kind  of 
an  entity,  and  hence  giving  no  support  to  the  notion  of  a  disem- 
bodied spirit,  in  the  extreme  sense  of  that  expression.  How 
much  matter  is  really  needed  to  exhibit  any  degree  of  life  } 

Let  us  turn  now  to  the  other  factor,  —  mind.  First  it  may  be 
remarked  that  there  is  no  tangible  evidence  of  the  existence  of 
mind  apart  from  some  kind  of  a  material  structure.  I  suppose 
there  is  no  one  now  who  would  imagine  that  in  the  develop- 
ment of,  say  a  chicken,  there  came  a  time  in  the  physical  and 
chemical  changes  going  on  in  a  warm  t^^  when  it  was  in 
some  superphysical  way  endowed  with  what  we  call  mind  in 
any  degree,  so  that  one  could  say,  now  this  growing  thing  is 
without  mind,  and  the  next  instant,  now  this  growing  thing 
has  a  mind.  If  mental  endowment  be  not  a  part  of  the 
physical  process  just  as  necessary  under  the  conditions  as  any 
other  part  of  the  process,  then  one  must  say  at  some  instant, 
7tow  it  has  been  endowed.  The  chicken  in  the  ^g^  has  life, 
for  it  grows,  and  when  out  of  it  gives  evidence  of  intelligence 
of  no  mean  grade.  Whatever  its  grade,  it  is  the  outcome 
either  of  its  physical  constitution  or  else  there  has  been  a 
miracle  of  some  order.  Is  there  any  third  alternative  t  I 
know  of  none.  That  there  has  been  a  miraculous  phenomenon 
in  the  ^gg^  no  one  can  believe,  and  that  the  intelligence  is  the 
mere  outcome  of  physical  antecedents  few  want  to  believe. 
If    one    believes    that    humanity,    as    it    now    is,    is  traceable 


94  BIOLOGICAL   LECTURES. 

without  miracle  into  geologic  times,  that  in  some  kind  of 
a  way  all  degrees  of  intelligence  are  directly  related,  then 
what  in  its  degree  is  true  for  a  chicken  is  also  true  for 
man,  and  mental  endowment  is  no  more  miraculous  for  one 
than  the  other  ;  and  one  must  need  to  look  for  his  so- 
called  faculties  where  he  must  look  for  those  of  the  chicken 
or  the  dog,  namely,  as  the  outcome  of  the  original  endowment 
of  what  we  call  matter,  rather  than  as  a  supernatural  alliancQ 
with  matter  which  is  the  common  notion.  Already  enough  is 
known  as  to  the  material  dependence  of  the  mind  upon  the 
body  to  warrant  even  judicial  acts  to  be  based  upon  chemical 
analysis  of  bodily  products  ;  that  emotions  of  different  kinds 
yield  corresponding  chemical  substances.  Some  of  these  pro- 
ducts are  harmful  in  the  extreme,  some  poisonous,  while 
others  are  healthful  and  promotive  of  life.  Brain  building  is 
the  end  towards  which  this  new  science  is  reaching.  One  of 
its  axioms  is  that  the  mind  can  only  be  educated  through  the 
senses,  and  the  more  senses  and  the  better  they  are  developed 
the  more  mental  power.  Thinking  is  the  function  of  gray 
cellular  matter  that  covers  the  brain  like  the  rind  of  an  orange. 
Unconscious  thinking  vastly  exceeds  in  amount  our  conscious 
thinking.  When  thinking  and  doing  have  been  repeated  often, 
they  cease  to  be  conscious  acts,  —  they  become  automatic,  in- 
stinctive, and  seem  to  sink  out  of  conscious  personality ;  but 
they  may  be  summoned.  So  that  unconsciousness  makes  the 
most  part  of  our  lives.  The  individual  starts  with  a  bundle  of 
instincts,  that  is,  inherited  experiences,  all  unconscious,  but 
yet  the  product  of  consciousness  ;  and  consciousness  that  has 
all  come  from  and  through  nerve  action.  All  this  may  be  so, 
and  yet  the  question  still  could  be  asked,  are  mind  and  matter 
separable  }  One  might  point,  as  others  have  frequently  done, 
to  the  evidence  of  the  growth  and  decadence  of  the  mind  along 
with  the  growth  and  decadence  of  the  bodily  functions,  of  the 
impairment  of  mental  activity  and  quality  when  the  brain  or 
stomach  or  liver  is  impaired,  and  full  recovery  when  these  are 
brought  to  normal  conditions  again  ;  also  how  the  individual 
lives  over  in  himself  the  history  of  the  race,  as  a  mere  animal 
at  first,  then  a  savage,  and  lastly  as  an  intellectual  and  moral 


RELATIONS  BETWEEN  MIND   AND   MATTER.        95 

being,  —  a  condition  of  things  that  educational  theories  and 
practice  ignore  or  overlook  when  they  attempt  to  make  a  moral 
and  intellectual  being  out  of  one  in  his  savage  stage  of  exist- 
ence, as  if  one  should  try  to  make  the  caterpillar  live  on  the 
honey  of  flowers  and  fly,  when  as  yet  it  had  neither  the 
instincts  nor  machinery  for  such  a  life.  Feed  him  what  he 
wants  and  can  digest,  protect  him  from  enemies  of  all  sorts, 
and  let  him  otherwise  alone.  If  nature  intended  him  to  fly, 
his  wings  are  growing,  though  they  may  be  folded  so  as  not  to 
be  discerned  and  no  use  is  made  of  them.  Let  them  alone. 
If  she  did  not  thus  intend  him  to  fly,  no  food  nor  training  nor 
painstaking  will  give  him  wings  and  he  will  never  fly.  This  is 
a  by-path. 

To  everyone  who  has  thought  and  read  on  this  subject  of  the 
relation  of  mind  to  the  bodily  organism,  especially  in  the  last 
few  years,  there  appears  at  once  the  question  of  the  relation  of 
the  doctrine  of  the  conservation  of  energy  to  mental  action, 
the  question  of  free  will  and  the  question  of  automatism.  I 
have  not  heard  that  any  one  actually  disputes  the  doctrine  of 
the  conservation  of  energy,  which  means  that  energy  is  not 
created  nor  annihilated  by  any  kind  of  a  process  known  to 
us.  Let  me  quote  the  words  of  Hoffding  in  his  OiUlines  of 
Psychology  as  bearing  on  this  point  :  *'  In  the  nature  of  the 
case  only  four  possibilities  can  be  conceived  :  (i)  either  con- 
sciousness and  brain,  mind  and  body  act  one  upon  the  other 
as  two  distinct  beings  or  substances,  (2)  or  the  mind  is  only  a 
form  or  product  of  the  body,  (3)  or  the  body  is  only  a  form  or 
product  of  one  or  several  mental  beings,  or  finally,  (4)  mind 
and  body,  consciousness  and  brain  are  evolved  as  different  forms 
of  expression  of  one  and  the  same  being."  He  then  presents 
the  arguments  pro  and  con  on  each  of  these,  and  at  last  thus 
concludes  :  *'  Only  the  last  or  the  fourth  possibility  then  seems 
to  be  left.  We  have  no  right  to  take  mind  and  body  for  two 
beings  or  substances  in  reciprocal  interaction.  On  the  contrary, 
we  are  impelled  to  conceive  the  material  interaction  between 
the  brain  and  nervous  system  as  an  outer  form  of  the  inner 
ideal  unity  of  consciousness.  Both  parallelism  and  propor- 
tionality between    the  activity  of   consciousness  and  cerebral 


96  BIOLOGICAL   LECTURES. 

activity  point  to  an  identity  at  bottom,"  and  he  italicizes  identity. 
Such  statements  from  such  a  source  show  that  even  psycholo- 
gists of  the  experimental  type  have  been  driven  to  conclude  that 
mentality  and  physical  activity  are  not  different  things,  but 
opposite  sides  of  the  same  thing,  which  is  saying  in  another 
way  that  mind  is  as  much  a  function  of  matter  as  is  gravitation, 
or  as  magnetism  is  of  iron,  —  cannot  be  created  nor  destroyed 
nor  isolated,  but  may  be  obscured  in  various  ways.  To  say 
that  one  cannot  conceive  how  mind  can  be  so  related  is  not  to 
say  much.  Can  any  one  say  he  can  conceive  how  mind,  as  he 
imagines  it,  can  exist  in  a  body  at  all }  And  does  one  need  to 
wait  until  any  matter  is  fully  explained  before  he  can  assent  to 
what  is  known  about  it  t  Thus  the  existence  of  dynamos  and 
motors  and  electric  lights  and  telegraphs  and  telephones  is  in 
itself  sufficient  to  prove  that  we  know  a  great  deal  about  elec- 
tricity, the  conditions  for  its  generation  and  utilization  ;  and 
when  one  adds  to  these  the  knowledge  that  dynamos  and 
motors  can  be  made  at  will,  having  an  efficiency  of  96  or  97^, 
he  has  as  high  a  guarantee  as  one  can  have  for  anything  in 
this  world  that  no  man  hereafter  can  improve  on  our  electrical 
apparatus  by  as  much  as  5^,  and  all  this  without  pretending 
to  know  or  even  guess  how  it  is  that  electricity  can  do  any- 
thing, much  less  have  a  knowledge  of  its  ultimate  nature. 
These  may  come  in  due  time.  Meanwhile  one  need  not  be 
skeptical  as  to  how  much  is  known  —  really  known  —  about  it, 
because  he  cannot  an^jver  the  very  last  question  which  may  be 
asked  about  it. 

What,  then,  is  the  present  status  of  the  question  }  In  our 
experience  mind  is  associated  with  matter  always,  life  as  we 
know  it  is  always  associated  with  a  particularly  complex  chem- 
ical substance  ;  and  when,  for  any  reason,  this  substance  of 
life  is  disintegrated,  the  evidence  of  life  goes  too.  The  more 
complicated  the  material  organism,  the  more  complicated  the 
manifestations  of  life  and  of  mind. 

The  delight  in  the  consciousness  of  existence  has  led  man  to 
wish  for  its  continuance  and  to  cast  about  for  evidence  of  it. 
The  apparent  destruction  of  mind  with  the  disintegration  of 
the  body  has  led  men  to  think  there  must  be  some  fallacy 


RELATIONS  BETWEEN  MIND   AND   MATTER.        97 

somewhere ;  and  so  they  have  asserted  that  the  body  is  but  a 
temporary  habitat  for  the  mind,  or  soul,  as  it  is  often  called, 
and  that  the  soul  could  and  did  exist  independent  of  matter 
in  any  of  its  embodiments,  so  the  conscious  being  has  been 
imagined  as  an  immaterial  something,  very  much  as  heat  and 
light  and  electricity  have  been  supposed  to  be  immaterial 
somethings.  By  and  by  heat  and  light  and  electricity  were 
each  shown  to  be  no  such  kind  of  things,  and  as  having  no 
existence  apart  from  ordinary  matter.  After  that,  vital  force 
as  differing  from  chemical  and  physical  forces  was  dispensed 
with,  and  next  both  biologist  and  physicist  agree  that  life  is,  in 
all  probability,  but  a  function  of  ordinary  matter;  and  lastly 
the  psychologist  brings  in  as  his  return  that  mind  and  matter 
are  but  the  two  sides  of  the  same  reality.  This  does  not  mean 
what  it  has  generally  been  taken  to  mean,  but  exactly  the 
opposite.  It  has  been  held  and  taught  by  many  that  to  asso- 
ciate either  life  or  mind  with  matter  as  a  necessary  adjunct 
was  pure  materialism.  Some  have  thought  that  if  the  doctrine 
of  the  conservation  of  energy  were  true  or  were  admitted  to  be 
true,  'then  life  would  be  correlated  with  the  other  forces  as 
they  are  correlated  with  each  other,  so  that  whenever  one 
appeared  it  was  at  the  expense  of  and  destruction  of  some 
other,  —  as  when  heat  energy  is  changed  into  work  or  into 
electrical  energy.  But  the  analogy  is  wrong.  It  would  be 
nearer  correct  to  liken  it  to,  say  magnetism  of  a  piece  of  iron. 
For  convenience  we  say  we  magnetize  a  piece  of  iron.  In 
reality  we  do  nothing  of  the  sort,  —  the  iron  is  already  as  mag- 
netic as  it  can  be ;  all  we  do  is  to  arrange  its  molecules  so  that 
the  inherent  magnetism  of  each  one  will  act  in  the  same  direc- 
tion as  all  the  rest.  There  is  as  much  magnetism  in  a  piece  of 
iron  at  one  time  as  at  another;  we  cannot  change  that.  To 
carry  out  the  analogy,  if  one  would  suppose  that  when  the 
atoms  and  molecules  of  matter  are  of  proper  sort  and  arranged 
in  a  proper  way,  as  they  are  in  the  substance  called  protoplasm, 
then  the  individual  living  characteristics  of  each  could  manifest 
themselves  in  the  way  exhibited  by  a  living  thing,  not  because 
there  was  a  new  force  or  being  or  entity  not  there  before,  but 
because  all  could  work  in  concert  to  the  same  end,  while  they 


98  BIOLOGICAL   LECTURES. 

cannot  under  ordinary  physical  conditions.  In  other  words, 
there  is  nothing  which  was  not  there  before.  One  is  not  get- 
ting out  of  the  machine  what  was  not  in  it,  but  what  was  in  it, 
and  there  is  no  quarrel  with  the  doctrine  of  the  conservation 
of  energy.  That  doctrine,  if  true,  would  only  insure  conti- 
nuity, regularity,  and  certainty  of  dependent  relations. 

Still  more  than  this.  It  is  important  to  recognize  how  much 
energy  there  may  be  in  a  microscopic  mass  of  matter,  and  also 
what  an  amount  of  intelligence  may  be  there  too  !  Think  of  the 
intelligence  shown  by  a  common  ant :  he  lives  in  a  community 
having  common  interests,  and  where  the  duties  of  individuals 
are  appointed  and  faithfully  executed,  —  duties  of  securing 
food,  of  protecting  and  caring  for  the  young,  of  defending  the 
community  as  a  whole.  They  make  war,  and  slavery  is  the 
price  of  peace  ;  they  have  a  language  of  some  sort  and  a 
degree  of  civilization  superior  to  some  tribes  of  men,  and  all 
this  the  outcome  of  a  brain  so  small  that  no  balance  we  have 
is  delicate  enough  to  weigh  it.  It  is  plain  proof  that  if  mind 
does  require  some  material  habitat,  its  requirements  are  not 
excessive ;  indeed,  if  one  will  remember  that  in  a  mass  of  mat- 
ter only  the  thousandth  part  of  an  inch  in  diameter  there  are 
thousands  of  millions  of  atoms,  he  will  see  that  the  possibility 
of  variety  of  form,  of  position,  and  of  relations  is  almost  infinite, 
and  if  mind  depended  upon  these  in  any  measure,  the  possi- 
bilities would  also  be  nearly  infinite.  There  is  nothing  in  all 
this  that  implies  that  what  is  called  death  ends  all,  —  rather  the 
contrary,  for  it  is  plainly  in  accordance  with  all  we  know  to 
hold  that  the  so-called  ego  is  a  real  material  thing,  a  mole- 
cule too  minute  to  be  seen  or  identified,  but  which  absorbs  all 
experiences  and  holds  them  as  memory,  which  can  be  disso- 
ciated from  the  rest  of  the  body,  but  which  cannot  itself  be 
disrupted  any  more  than  atoms  of  the  ordinary  sort  can  be, 
which  is  as  durable  as  we  believe  others  to  be,  but  differs  from 
them  chiefly  in  having  been  ediLcated  by  being  in  such  a  posi- 
tion that  all  sorts  of  reactions  took  place  in  its  environment 
and  in  itself. 

Formerly  mind  was  supposed  to  be  honored  by  degrading 
its  material  habitat;  now  we  are  confronted  with  the  knowledge 


RELATIONS  BETWEEN  MIND   AND   MATTER.        99 

that  matter  is  not  what  it  was  thought  to  be  or  to  be  like,  that 
its  nature  is  as  mysterious  as  is  the  nature  of  mind.  In  expe- 
rience we  find  the  two  always  associated.  Experience  leads  to 
the  belief  that  one  of  these  is  imperishable,  and  we  make  it 
a  corner-stone  in  physical  science ;  and  my  thesis  is  that  mind 
can  no  more  be  sloughed  off  from  it  than  can  gravity  or  mag- 
netism or  any  other  of  its  inherent  qualities. 


SEVENTH     LECTURE. 


ON    THE    PHYSICAL    BASIS    OF    ANIMAL    PHOS- 
PHORESCENCE.i 

S.  WATASJg. 

Whatever  view  we  may  take  as  to  the  nature  of  vitality,  it 
is  evident  that  we  can  know  life  only  through  the  physical, 
chemical,  or  mechanical  manifestations,  which  an  organism 
displays  at  various  phases  of  its  existence.  Our  organs  of 
sense,  which  supply  directly  or  indirectly  the  material  of 
human  knowledge  of  both  the  animate  and  inanimate  world, 
are  only  related  to  force,  or  are  set  into  a  state  of  excitation 
by  motion  of  certain  kinds,  which  we  call  a  stimulus.  What- 
ever view,  therefore,  a  biological  philosophy  may  lead  us  to 
accept  in  regard  to  the  ultimate  nature  of  life,  our  primary 
step  in  the  study  of  vitality  must  begin  with  the  examination 
of  its  material  manifestations. 

Among  many  physical  phenomena  manifested  by  the  living 
organism  there  are  few  so  striking,  and  none  appear  so  isolated, 
as  the  phenomena  of  the  emission  of  light.  Thus,  Darwin, 
in  his  discussion  of  some  special  difficulties  of  the  theory  of 
natural  selection,  says  :  **  The  luminous  organs  which  occur  in 
a  few  insects,  belonging  to  widely  different  families,  and  which 
are  situated  in  different  parts  of  the  body,  offer,  under  our 
present  state  of  ignorance,  a  difficulty  almost  exactly  parallel 
with  that  of  the  electric  organs,"  and  "it  is  impossible  to 
conceive  by  what  steps  these  wondrous  organs  have  been 
produced."  ^ 

1  The  present  paper  is  part  of  three  lectures  on  Animal  Phosphorescence, 
delivered  at  the  Marine  Biological  Laboratory  at  Woods  HoU,  during  the  sum- 
mers of  1894  and  1895,  ^"*^  elsewhere.  A  monographic  account  of  the  subject, 
with  a  full  bibliography,  will  be  presented  in  the  near  future. 

2  Darwin  :  Origin  of  Species.  « 


I02  BIOLOGICAL   LECTURES. 

But  viewed  from  the  standpoint  of  cell  physiology,  the  phe- 
nomena of  animal  phosphorescence  is  the  result  of  physico- 
chemical  changes  in  the  living  protoplasm,  probably  of  the 
same  nature  as  that  of  heat  production,  the  only  peculiarity  of 
the  former  being  that  it  manifests  itself  in  such  a  form  as  to 
affect  the  most  potent  of  our  special  senses,  —  the  sense  of 
sight,  —  and  the  latter,  the  sense  of  temperature. 

On  a  priori  ground  it  is  easily  conceivable  that  the  animal 
that  produces  heat,  as  all  animals  can,  may  just  as  well  produce 
light  under  certain  circumstances,  for  both  are  but  the  mani- 
festations of  the  same  energy,  and  can  be  produced  by  essen- 
tially the  same  physico-chemical  antecedents. 

The  production  of  light  by  the  living  organism  becomes  still 
more  interesting,  and  appears  unique  when  we  remember  that 
the  light  thus  produced  is  not  accompanied  by  any  sensible 
heat. 

"  You  gaudy  glow-worms,  carrying  seeming  fire, 
Yet  have  no  heat  within  ye  !  "  ^ 

This  difference  between  the  light  produced  by  the  activity 
of  the  living  organism  and  by  the  purely  artificial  process  has 
also  been  pointed  out  by  the  natural  philosopher,  Robert  Boyle. 
In  one 2  of  his  several  contributions  on  the  subject  he  says: 
'*  That  whereas  a  coal,  as  it  burns,  sends  forth  store  of  smoke 
or  exhalations,  luminous  wood  does  not  so  ";  and  "that  whereas 
a  coal  in  shining  wastes  itself  at  a  great  rate,  shining  wood  does 
not";  and  ''that  a  quick  coal  is  actually  and  vehemently  hot, 
whereas  I  have  not  observed  shining  wood  to  be  so  much  as 
sensibly  lukewarm."^ 

The  same  peculiarity  in  the  light  of  the  living  substance  has 
been  recognized  by  Faraday,  Matteucci,  Young,  Langley,  and 
Very,  and  by  the  last  two  it  has  been  made  the  subject  of  a 
beautiful  research  within  recent  years. 

1  Fletcher:  The  Elder  Brother,  act  iv,  sc.  i,  1637. 

2  R.  Boyle  :  Observations  and  Trials  about  the  Resemblances  and  Differences 
between  a  Burning  Coal  and  Shining  Wood,  Phil.  Trans.,  No.  XXXII,  605,  1667- 
1668. 

*  It  is  hardly  necessary  to  say  that  Boyle  was  not  aware  of  the  fact  that  the 
luminosity  of  the  shining  wood  is  caused  by  the  activity  of  the  living  organism. 


BASIS   OF  ANIMAL   PHOSPHORESCENCE.  1 03 

Readers  of  the  Life  of  Faraday  will  notice  what  a  lively 
interest  he  took  in  the  luminous  phenomena  of  the  fire-fiy  and 
the  glow-worm.  The  journaP  he  kept  during  his  travel  over 
the  continent  with  Sir  Humphry  Davy  in  18 14,  when  Faraday 
was  twenty-two  years  old,  makes  frequent  mention  of  his  experi- 
ments with  the  luminous  phenomena  of  the  fire-fly  and  the  glow- 
worm. I  quote  him  at  length  because  he  correctly  surmised  all 
the  results  of  his  later  workers,  and  also  because  his  unassuming 
but  remarkable  record  of  his  observations  has  escaped  the  notice 
of  writers  on  animal  phosphorescence  subsequent  to  the  publi- 
cation of  Faraday's  Life.     (Italics  are  mine.) 

"  On  the  way  home  many  fire-flies  appeared,  emitting  their 
transient  light .^  I  caught  several ;  and  on  arriving  at  the 
house  endeavored  to  ascertain  whether  the  luminous  appearance 
depended  on  the  life  of  the  fly.  I  found  one  apparently  dead ; 
and  separating  the  part  which  emitted  light  from  the  rest  of 
the  body,  it  appeared  filled  with  a  white  glutinous  matter, 
which,  when  extended  and  exposed  to  the  air,  shone  for  about 
a  minute. 

''  I  killed  a  fly  suddenly,  and  separated  the  matter.  It  was 
shining  at  the  moment  I  killed  it ;  but  when  dead  it  ceased  to 
shine.  On  separating  the  part  and  exposing  it  to  the  air  it 
irrimediately  shone  brightly  as  when  attached  to  the  fly,  and 
over  the  whole  surface,  although  only  the  section  was  exposed 
to  the  air.  It  at  length  became  dim ;  but  on  compressing 
it,  and  exposing  a  fresh  part  to  the  air,  it  shone  brightly 
as  at  first,  and  thus  it  continued  luminous  for  above  forty 
minutes.  At  last  it  became  totally  extinct ;  and  the  same 
effect  took  place  with  other  flies  treated  in  the  same  manner. 
It  is  probable^  from  the  intermitting  and  regular  appear- 
ance of  the  lighty  that  it  has  a  dependence  on  the  respiration ; 
and  at  least  it  is  evident  that  air  is  suffi,cient  to  cause  this 
matter  {probably  a  secretion)  to  shine.  No  heat  was  sensible 
to  the  hands  or  to  the  underlip  {the  most  delicate  part  of  the 
body)!' 

1  Dr.  Bence  Jones  :  Life  and  Letters  of  Faraday,  Vol.  I,  1870,  pp.  90,  91,  125, 
141,  142,  144-146. 

^  Friday,  June  3,  1814  (Terni),  Italy,  pp.  141,  142. 


104  BIOLOGICAL   LECTURES. 

In  his  entry  '^  Sunday,  July  lo,  1814,  Geneva,"  Faraday  de- 
scribes his  experiments  on  glow-worms. 

''This  evening  many  glow-worms  appeared,  and  of  four 
which  I  had  put  in  a  tumbler  with  green  leaves,  two  shone 
very  brightly.  I  separated  the  luminous  part  of  one  in  full 
vigor  from  the  body.  It  soon  faded,  and  in  about  ten  minutes 
ceased  to  emit  light ;  but  on  pressing  it  with  a  knife,  so  as  to 
force  the  matter  out  of  the  skin,  it  again  became  luminous,  and 
continued  to  shine  for  two  hojirs  brightly.  One  I  found  on  the 
floor  crushed  unawares  by  the  foot.  I  separated  the  luminous 
part  of  this  insect,  and  left  it  on  paper.  It  shone  with  undi- 
minished luster  the  whole  evening,  and  appeared  not  at  all  to 
have  suffered  in  its  power  of  emitting  light  by  the  mixture  and 
confusion  of  its  parts,  so  that  it  appears  to  depend  more  upon  the 
chemical  nature  of  the  substance  than  upoji  the  vital  powers  of 
the  animal ;  but  at  the  same  time,  it  appears,  from  the  variations 
in  splendor,  accompanied  by  motions  i7i  the  living  animal,  that  it 
may  be  much  influenced  or  ^nodified  by,  or  in  some  7nanner 
submitted  to,  the  powers  of  the  worm. 

"The  matter  which  appears  to  fill  the  hinder  part  of  the 
body  in  the  shining  season  is  yellowish-white,  soft,  and  glutinous. 
It  is  insoluble,  apparently,  in  water  or  in  alcohol.  It  does  not 
immediately  lose  its  power  of  shining  in  water.  Heat  forces 
out  a  bright  glow,  and  then  it  becomes  extinct ;  but  if  not 
carried  too  far,  the  addition  of  moisture  after  a  time  revives  its 
power.  No  motion  or  mixture  seems  to  destroy  its  power 
whilst  it  remains  fresh  and  moist,  but  yet  a  portion  thus  rubbed 
sooner  lost  its  light  than  a  portion  left  untouched.  The  time 
of  its  continuance  in  a  luminous  state  was  very  various,  and 
perhaps  depends  upon  the  state  of  the  worms  from  which  it 
was  taken.  The  death  of  the  worm  seemed  to  have  no  imme- 
diate effect  upon  the  illumination  of  the  hinder  part ;  and  with 
respect  to  the  length  of  time  that  it  continued  to  shine  after- 
wards, it  seemed  indifferent  whether  it  was  left  on  the  body  or 
taken  off;  but  when  extinct,  exposure  of  the  interior  to  air 
always  caused  a  fresh  emanation  of  light.  I  found  a  worm 
which  emitted  light  from  a  very  small  part  of  the  body,  and 
very  feebly,  and  for  a  very  short  time  together.     The  worm 


BASIS   OF  ANIMAL   PHOSPHORESCENCE.  1 05 

was  larger  than  the  ordinary  species,  and  had  more  divisions. 
The  power  of  emitting  light  in  the  ordinary  worm  seemed 
proportionate  to  the  age  of  the  animal." 

Monday,  Ilth.  "  The  matter  of  the  worms  referred  to  yes- 
terday still  shines.  It  was  detached  from  the  animal  at  8.24, 
and  still  promises  to  emit  light  much  longer." 

Tuesday,  l2tJi.  "The  matter  was  luminous  this  day  at 
10.41,  though  faintly,  and  at  twelve  o'clock  no  light  could 
be  perceived.  The  matter  had  become  quite  dry  and  semi- 
transparent,  but  the  addition  of  water  produced  no  particular 
effect." 

Faraday's  results  may  be  briefly  stated  as  follows  :  — 

(i)  There  is  a  chemical  substance  in  the  glow-worm  and  the 
fire-fly  which  has  power  to  shine  independently  of  the  life  of 
the  insect. 

(2)  This  substance  is  probably  a  secretion  of  the  insect. 

(3)  The  shining  depends  on  the  respiration,  and  the  air  is 
enough  to  cause  this  substance  to  shine. 

(4)  From  the  variation  in  the  splendor  of  light,  accompanied 
by  motions  in  the  living  animal,  the  animal,  as  a  whole,  has 
in  some  way  the  control  of  the  external  manifestation  of  light. 

Matteucci,  also,  in  his  letter  to  Duma,^  and  elsewhere,^  came 
to  the  same  conclusion  as  Faraday,  and  says  :  ''  In  the  glow- 
worm there  is  a  substance  which,  without  any  sensible  heat, 
diffuses  a  light  that  does  not  require  the  integrity  of  the 
animal  and  of  its  living  state  in  order  to  manifest  itself  with 
its  peculiar  properties." 

It  will  contribute  to  the  clearness  of  the  whole,  if,  instead  of 
examining  various  other  theories  proposed  from  time  to  time, 
in  the  nature  of  animal  light,  I  dwell  briefly  here  on  the  rela- 
tion of  objective  and  subjective  aspects  of  what  we  call  the 
sensation  of  light  and  of  heat,  or  the  relation  of  various  kinds 
of  ether  vibrations  to  the  specific  energy  of  senses. 

We  habitually  associate  the  sensation  of  light  with  that  of 
heat,  so  that  it  becomes  almost  impossible  to  separate  them  in 

1  Carlo  Matteucci:  Sur  la  phosphorescence  du  Lampyre  d'ltalie  (L.  Italica). 
CompL  Rend.  XVII,  p.  309,  August  14,  1843. 

2  Matteucci :  Lectures  on  the  Physical  Phenomena  of  Living  Beings,  1848,  p.  165. 


I06  BIOLOGICAL   LECTURES. 

our  common  experience  ;  and  when  we  meet  with  such  a  phe- 
nomenon as  the  production  of  light  from  the  animal  tissue 
without  any  sensible  heat,  it  appears  as  if  it  were  a  totally 
isolated  physiological  phenomenon  with  no  parallel  in  the 
ordinary  activity  of  life. 

According  to  the  physicist,  however,  the  external  agent 
which  gives  rise  to  the  sensation  of  light  in  our  organism  is 
not  much  different  from  that  which  gives  rise  to  the  sensation 
of  heat.  Heat  and  light  are  only  the  variations  of  the  same 
radiant  energy.  There  is  an  absolute  continuity  in  the  nature 
of  the  two  phenomena  —  the  vibrations  of  ether. 

"When  the  wave-length  is  greater  than  812  millionths  of  a 
millimeter  no  luminous  effect  is  produced  on  the  eye,  though 
the  effect  on  the  thermometer  may  be  very  great.  When  the 
wave-length  is  650  millionths  of  a  millimeter  the  ray  is  visible 
as  a  red  light,  and  a  considerable  heating  effect  is  observed. 
But  when  the  wave-length  is  500  millionths  of  a  millimeter,  the 
ray,  which  is  seen  as  a  brilliant  green,  has  much  less  heating 
effect  than  the  dark  or  the  red  rays,  and  it  is  difficult  to  obtain 
strong  thermal  effects  with  rays  of  smaller  wave-lengths,  even 
when  concentrated."  ^ 

The  light  and  heat  are  so  very  different  to  us  because  we 
perceive  them  with  different  organs  of  sense.  The  heat  radia- 
tion, or  the  waves  of  ether  which  have  most  heating  effect,  we 
perceive  with  the  organ  of  temperature  sense,  while  a  similar 
radiation,  with  different  wave-lengths,  which  have  most  liLmi- 
nous  effect,  we  perceive  with  the  organ  of  sight. 

The  difference  between  heat  and  light,  therefore,  "  is  purely 
subjective,  depending  on  our  organization  and  not  on  the  nature 
of  external  objects."  ^  There  is  an  absolute  continuity  in  the 
nature  of  external  disturbances  which  create  in  us  the  sensa- 
tions of  heat  and  of  light,  the  difference  between  them  being 
that  of  degree  and  not  of  kind.  Expressed,  therefore,  in  terms 
of  visual  sensation,  heat  is  invisible  light ;  and  light,  expressed 
in  that  of  temperature  sense,  is  heat  with  a  very  little  heating 
effect. 

1  Clerk-Maxwell  :  Theory  of  Heat,  Chap.  XVI.,  On  Radiation,  p.  239. 

2  Stokes:  On  Light,  p.  266. 


BASIS   OF  ANIMAL   PHOSPHORESCENCE.  1 07 

If  our  organs  concerned  in  the  sensation  of  light  were  some- 
what different  from  what  they  are  now,  it  is  possible  that  what 
appears  as  luminous  may  have  no  such  effect,  and  what  appears 
as  dark  may  even  appear  as  luminous.  *'  It  is  quite  conceivable 
that  animals  might  exist  to  which  obscure  heat  rays  might  be 
visible,  and  to  which  man  and  mammals  generally  would  appear 
constantly  luminous."  ^ 

The  animal  organism  is  an  actual  apparatus  of  combustion, 
in  which  carbon  compounds  are  constantly  burnt,  and  from 
which  carbonic  acid  is  always  escaping.  There  is  no  difBculty 
in  conceiving  that  organisms  which  produce  heat  in  this  way 
may  under  certain  circumstances  produce  light,  if  the  combus- 
tion of  the  material  in  the  body  could  be  carried  on  in  such  a 
manner  as  to  impart  a  more  rapid  vibration  to  the  surrounding 
ether  than  that  which  results  in  the  production  of  thermal 
radiation. 

The  vibration  of  ether  thus  produced  with  higher  frequency 
and  of  shorter  wave-lengths,  such  as  we  see  in  the  fire-fly, 
would  affect  the  organ  of  vision,  but  not  the  organ  of  tempera- 
ture. A7id  this  difference  of  result^  so  conspicuous  to  tis,  may  not 
imply  7nore  than  a  very  slight  variation  on  the  part  of  the  indi- 
vidual organism  at  the  start.  Nature  desires,  if  I  may  use 
such  an  expression,  nothing  but  light  in  such  an  organism  as 
the  fire-fly,  and  produces  this  with  the  least  possible  waste. 

That  this  is  a  legitimate  inference  may  be  shown  from  the 
several  works  of  physicists.  Several  years  ago  Professor 
Young  2  examined  the  spectrum  of  the  fire-fly  and  stated  his 
important  observations  in  the  following  form. 

*'  The  spectrum  given  by  the  light  of  the  commom  fire-fly  of 
New  Hampshire  {Photinus  ?)  is  perfectly  continuous,  without 
trace  of  lines  either  bright  or  dark.  It  extends  from  a  little 
above  Fraunhofer's  line  C  in  the  scarlet  to  about  F  in  the 
blue,  gradually  fading  at  the  extremities.  It  is  noticeable 
that  precisely  this  portion  of  the  spectrnm  is  composed  of  rays, 
tvJiicJi^  while  they  more  powerfnlly  than  any  others  affect  the 

1  Mosely:  Notes  by  a  Naturalist  on  H.  M.  S.  Challenger,  1892,  p.  512. 

2  C.  A.  Young  :  Spectrum  of  the  Fire-fly.  Amer.  Naturalist,  Vol.  Ill,  1870, 
p.  615. 


I08  BIOLOGICAL    LECTURES. 

organs  of  vision^  produce  hardly  any  thermal  or  actinic  effect.  In 
other  words,  very  little  of  the  e7iergy  expended  in  the  flash  of 
the  firefly  is  wasted.  It  is  quite  different  with  our  artificial 
methods  of  illumination.  In  the  case  of  an  ordinary  gaslight 
the  best  experiments  show  that  not  more  than  one  or  two  per 
cent  of  the  radiant  energy  consists  of  visible  rays,  the  rest  is 
either  invisible  heat  or  actinism  ;  that  is  lo  say,  over  ninety- 
eight  per  cent  of  the  gas  is  wasted  in  producing  rays  that  do 
not  help  in  making  objects  visible." 

Of  Professor  Langley  and  Mr.  Very's  more  recent  and  well- 
known  paper  *' On  the  Cheapest  Form  of  Light,"  ^  most  of  you  are 
doubtless  aware.  As  their  observations  are  the  most  accurate 
extant  on  the  physical  properties  of  animal  light,  it  will  not  be 
out  of  place  to  reproduce  here  at  length  the  essential  points  of 
their  conclusions,  as  well  as  some  of  their  instructive  state- 
ments on  the  concepts  of  radiant  energy,  which  underly  their 
experimental  inquiries. 

"We  recall,"  says  Professor  Langley,  "that  in  all  industrial 
methods  of  producing  light,  there  is  involved  an  enormous 
waste,  greatest  in  sources  of  low  temperature  like  the  candle, 
lamp,  or  even  gas  illumination  where,  as  I  have  already  shown,  it 
ordinarily  exceeds  ninety-nine  parts  in  the  one  hundred  ;  and 
least  in  sources  of  high  temperature  like  the  incandescent  light 
and  electric  arc,  where  yet  it  is  still  immense  and  amounts,  even 
under  the  most  favorable  conditions,  to  very  much  the  larger 
part"  (p.  97). 

"  It  is  now  universally  admitted  that  wherever  there  is  light, 
there  has  been  expenditure  of  heat  in  the  production  of  radia- 
tion existing  in  and  as  the  luminosity  itself,  since  both  are  but 
forms  of  the  same  energy;  but  this  visible  radiant  heat  which 
is  inevitably  necessary  is  not  to  be  considered  as  waste.  The 
waste  comes  from  the  present  necessity  of  expending  a  great 
deal  of  heat  in  invisible  forms  before  reaching  even  the  slight- 
est visible  result,  while  each  increase  of  the  light  represents  not 
only  the  small  amount  of  heat  directly  concerned  in  the  making 

1  S.  p.  Langley  and  F.  W.  Very  :  On  the  Cheapest  Form  of  Light,  from  Studies 
at  the  Allegheny  Observatory  with  Plates  III,  IV,  and  V.  The  American  Journal 
of  Science,  Third  Series,  Vol.  XL,  No.  236,  August,  1890. 


BASIS   OF  ANIMAL   PHOSPHORESCENCE.  109 

of  the  light  itself,  but  a  new  indirect  expenditure  in  the  produc- 
tion of  invisible  calorific  rays.  Our  eyes  recognize  heat  mainly 
as  it  is  conveyed  in  certain  rapid  ethereal  vibrations  associated 
with  high  temperatures  without  passing  through  the  interme- 
diate low  ones  ;  so  that  if  the  vocal  production  of  a  short  atmos- 
pheric vibration  were  subject  to  analogous  conditions,  a  high 
note  could  never  be  produced  until  we  had  passed  through  the 
whole  gamut,  from  the  discontinuous  sounds  below  the  lowest 
bass,  up  successively  through  every  lower  note  of  the  scale  till 
the  desired  alto  was  reached. 

"There  are  certain  phenomena  long  investigated,  yet  little 
understood,  and  grouped  under  the  general  name  of  '  phospho- 
rescent,' which  form  an  apparent  exception  to  this  rule,  espe- 
cially where  nature  employs  them  in  the  living  organism,  for  it 
seems  very  difficult  to  believe  that  the  light  of  a  fire-fly,  .for 
instance,  is  accompanied  by  a  temperature  of  2000°  or  more 
Fahr.,  which  is  what  we  should  have  to  produce  to  gain  it  by 
our  usual  processes.  That  it  is,  however,  not  necessarily  impos- 
sible, we  may  infer  from  the  fact  that  we  can  by  a  known  physi- 
cal process  produce  a  still  more  brilliant  light  without  sensible 
heat,  where  we  are  yet  sure  that  the  temperature  exceeds  this. 
No  sensible  heat  accompanies  the  fire-fly's  light  any  more  than 
need  accompany  that  of  the  Geissler  tube  ;  but  this  might  be 
the  case  in  either  instance,  even  though  heat  were  there,  owing 
to  its  minute  quantity,  which  seems  to  defy  direct  investigation. 
It  is  VLSUdWy  assumed  With,  apparent  reason,  that  the  insect's  light 
is  produced  without  the  invisible  heat  that  accompanies  our 
ordinary  processes,  and  this  view  is  strengthened  by  study  of 
the  fire-fly's  spectrum,  which  has  been  frequently  observed  to 
diminish  more  rapidly  toward  the  red  than  that  of  ordinary 
flames.  Nevertheless  this,  though  a  highly  probable  and  rea- 
sonable assumption,  remains  assumption  rather  than  proof,  until 
we  can  measure  with  a  sufficiently  delicate  apparatus,  the  heat 
which  accompanies  the  light,  and  learn  not  only  its  quantity, 
but  what  is  more  important,  its  quality  "  (pp.  98,  99). 

Under  *'  Photometric  Observations,"  the  authors  continue : 
"  The  first  impression  in  viewing  the  light  of  the  Pyrophortis 
noctilucus  through  a  spectroscope  is  that  it  consists  essentially 


no  BIOLOGICAL   LECTURES. 

of  a  broad  band  in  the  green  and  yellow,  while  with  precaution 
we  see  this  extending  into  and  beyond  the  borders  of  the  blue 
and  orange,  but  not  very  greatly  farther,  and  these  have  been 
taken  by  previous  observers  as  its  absolute  limits.  No  one 
appears  to  have  experimentally  and  distinctly  answered  the 
question,  "  Would  the  light  not  extend  farther  were  it  bright 
enough  to  be  seen  ?  "  nor  has  it  been  proved  as  clearly  as 
might  be  desired  that  the  result  depends  on  the  quality  rather 
than  the  quantity  of  the  light,  or  given  conclusive  evidence 
that  if  the  light  of  the  insect  were  as  bright  as  that  of  the 
sun,  it  would  not  extend  equally  far  on  either  side  of  the 
spectrum. 

"  It  is  impossible  to  increase  the  intrinsic  brilliancy  by  any 
optical  device,  but  if  it  be  impossible  to  make  the  light  of  the 
insect  as  bright  as  that  of  the  sun,  it  is,  on  the  other  hand,  quite 
possible  to  make  the  light  of  the  sun  no  brighter  than  that  of 
the  insect,  and  this  would  appear  to  be  the  first  step  in  obtain- 
ing a  definite  proof  that  the  apparently  narrow  limits  of  the 
insect's  spectrum  are  due  to  the  intrinsic  quality  of  the  light, 
and  not  to  its  feeble  intensity.  The  only  conclusive  method  of 
determining  this  would  appear  to  be  to  balance  the  light  from 
the  insect  with  that  of  a  definite  portion  of  sunlight  by  any 
ordinary  photometric  device  ;  and  having  taken  this  sunlight 
as  nearly  equal  as  possible  to  that  of  the  insect,  though  certainly 
not  greater,  to  let  this  determined  quantity  fall  on  the  slit  of 
a  spectroscope  at  the  same  time  with  the  light  from  the  insect, 
two  spectra  being  formed  one  over  the  other  in  the  same  field 
and  at  the  same  time  "  (pp.  103,  104). 

After  detailing  a  number  of  experiments,  the  authors  state 
that  *'when  spectra  are  formed  from  two  equal  lights,  one  from 
the  sun,  the  other  from  the  insect,  the  latter's  spectrum  termi- 
nates both  at  an  upper  and  a  lower  limit,  at  which  the  solar 
light  is  still  conspicuous.  The  conclusion  follows  that  the 
insect  spectrum  is  lacking  in  rays  of  red  luminosity,  and  pre- 
sumably in  the  infra-red  rays,  usually  of  relatively  great  heat, 
or  that  it  seems  probable  that  we  have  here  light  withotit  heaty 
other  than  that  heat  which  the  luminosity  itself  comprises  and 
which  is  but  another  name  for  the  same  energy"  (p.  108). 


BASIS   OF  ANhMAL    PHOSPHORESCENCE.  I  I  I 

Under  ''Thermal  Observations"  the  authors  proceed  :  "To 
give  an  idea  of  the  amount  of  heat  at  our  disposition  for  experi- 
ment, and  of  the  actual  minuteness  of  the  radiation  which  pro- 
ceeds from  even  the  most  luminous  tropical  insect,  we  may  say 
that  if  that  rate  of  radiation  from  a  lamp-black  surface  i  square 
cm.  in  area,  which  represents  the  amount  of  heat  necessary  to 
raise  i  gram  of  water  to  i°  centigrade,  in  i  minute  {i.e,  one 
small  calorie),  be  taken  as  unity,  then  the  luminous  radiation  of 
the  fire-fly's  heat,  per  square  cm.,  of  exposed  luminous  surface, 
as  we  have  found,  is  about  0.0004  calorie  in  10  seconds,  and  the 
total  luminous  radiation  from  the  most  powerfully  illuminating 
light  spot  of  the  insect  (the  abdominal  one)  will  not  exceed 
0.00007  calorie  in  the  same  time.  But  a  small  portion  of  this 
could  fall  upon  the  bolometer,  and  that  which  actually  reached 
it  during  the  time  (10  seconds)  required  for  each  observation  was 
sufficient  only  to  affect  an  ordinary  mercurial  thermometer 
having  a  bulb  i  cm.  in  diameter  by  rather  less  than  0.00000023, 
or  by  less  than  1/400000  of  one  degree  centigrade"  (pp.  108, 
109). 

"  Resuming,  then,  what  we  have  said,  we  repeat  that  nature 
produces  this  cheapest  light  at  about  one  four-hundredth  part 
of  the  cost  of  the  energy  which  is  expended  in  the  candle-flame, 
and  at  but  an  insignificant  fraction  of  the  cost  of  the  electric 
light  or  the  most  economic  light  which  has  yet  been  devised  ; 
and  that  finally  there  seems  to  be  no  reason  why  we  are  for- 
bidden to  hope  that  we  may  yet  discover  a  method  (since  such 
a  one  certainly  exists  and  is  in  use  on  a  small  scale)  of  obtain- 
ing an  enormously  greater  result  than  we  now  do  from  our 
present  ordinary  means  for  producing  light"  (p.  112). 

The  light  emitted  by  the  living  organism  differs  very  much 
in  color  in  different  animals,  and  even  in  the  same  animal  at 
different  periods  ;  green  has  been  noticed  in  the  glow-worm, 
fire-flies,  some  brittle-stars,  centipedes,  and  annelids  ;  blue  is 
seen  in  the  Italian  fire-fly  ;  blue  and  light-green  are  the  pre- 
dominant colors  exhibited  by  marine  animals  ;  the  beautiful  Gir- 
dle of  Venus,  some  species  of  Salpa,  and  Cleodora  appear  red ; 
Pavonaria  and  other  gorgonids  are  lilac  ;  and  one  hemiptera,  Ful- 
gora,   is  said  to  emit  a  purple  light.      One  very  remarkable 


112  BIOLOGICAL   LECTURED. 

Appendicularia  showed  in  one  individual  first  red^  then  blue^ 
and  finally  green}  This  remarkable  property  seems  to  be  pos- 
sessed by  other  tunicates,  for  Huxley  ^  states  in  his  well-known 
paper  on  Pyrosoma,  quoting  Peron,  that  Pyrosoma  exhibited 
movements  of  alternate  contraction  and  dilatation  at  regular 
intervals  ;  and  that  each  contraction  was  accompanied  by  the 
development  of  a  luminosity,  which,  when  at  its  brightest,  was 
red^  but  in  dying  away  passed  through  shades  of  orange,  green, 
and  blue.  Newport  ^  also  noticed  a  change  in  the  color  of  light 
emitted  by  the  glow-worm  at  the  end  of  the  season  from  that 
at  the  beginning.  I  have  learned  in  the  study  of  several  species 
of  fire-flies,  in  the  neighborhood  of  Woods  Holl  laboratory,  to 
distinguish  them  at  a  distance  by  the  color  of  their  light, 
which,  though  slight,  is  still  quite  characteristic  of  the  species. 

The  difference  in  color,  when  exhibited  by  different  organ- 
isms, is  probably  due  to  some  slight  chemical  differences  in  the 
light-giving  substance.  It  may  be  supposed  that  under  the 
influence  of  oxygen,  the  molecules  of  the  given  photogenic  sub- 
stance are  set  in  vibration,  the  rate  of  vibration  depending  on 
and  being  characteristic  of  the  particular  species.  And  in  those 
cases  where  a  series  of  colors  are  displayed  in  succession  by  the 
one  and  the  same  organism,  it  may  be  supposed  to  be  due  to 
either  of  two  causes  :  (i)  the  same  photogenic  substance  is  agi- 
tated with  different  degrees  of  frequencies  at  different  periods 
in  the  life  of  the  organism,  or  (2)  a  series  of  photogenic  sub- 
stances are  produced,  each  one  of  the  series  representing  a  stage 
in  the  chemical  metamorphosis  of  the  substance.  Without 
some  definite  chemical  knowledge  on  the  nature  of  such  photo- 
genic substances,  however,  it  is  useless  to  make  any  conjecture 
at  present. 

Nor  is  it  easy  to  offer  any  plausible  explanation  as  to  the  use 
of  such  light  to  the  organism,  which  will  apply  with  equal  force 
to  all  cases.     We  may  say  this  much,  however,  that  if  heat  inci- 

1  The  above  is  taken  from  W.  E.  Hoyle's  article  Phosphorescence,  in  the 
Encydopcedia  Brittanica,  Vol.  XVIII,  1885. 

2  Huxley  :  On  the  Anatomy  and    Development  of  Pyrosoma.     Phil.  Trans., 

1859. 

8  Newport :  On  the  Natural  History  of  Glow-worms.  Pi-oc.  Lin.  Soc,  Vol.  I, 
1857. 


BASIS   OF  ANIMAL   PHOSPHORESCENCE.  113 

dentally  produced  at  first  as  a  result  of  some  necessary  chemical 
changes  in  the  body  may  be  utilized  in  the  course  of  the  race 
history  of  an  organism  (as  among  birds  which  use  heat  evolved 
by  the  metabolism  of  their  tissue  for  the  process  of  incubation), 
it  is  equally  conceivable  that  light  incidentally  produced  as  the 
result  of  a  necessary  combustive  process  of  life  may  eventually 
be  utilized  in  the  race  history  of  some  species,  and  thus  that 
which  is  an  end  in  one  organism  may  become  the  means  to  a 
remoter  end  in  another  organism.  The  mere  fact  that  in  some 
animals  the  light  is  of  no  apparent  use  to  them  is  no  reason  to 
doubt  that  it  may  be  of  some  use  to  others,  in  which  the  pro- 
duction of  light  becomes  the  end  and  purpose  of  some  definite 
structure,  and  is  even  brought  in  connection  with  the  mechanism 
of  the  will. 

While  the  production  of  light  may  be  regarded  as  belonging 
to  the  same  ultimate  cause  as  that  of  heat,  the  proximate  cause 
of  the  luminosity  in  the  animal  kingdom  may  be  due  to  a  variety 
of  secondary  circumstances. 

Thus  (i)  an  organism  may  appear  brilliant  in  the  dark,  owing 
to  the  presence  of  luminous  bacteria  in  the  tissue.^  In  such  a 
case,  the  luminosity  of  the  organism  may  be  considered  as  a 
pathological  phenomenon. 

In  another  instance  (2)  the  organism  may  appear  luminous 
also  on  account  of  the  luminous  bacteria  which  live  in  a  sym- 
biotic fashion  in  the  tissue  of  the  organism,  but  this  cannot  be 
called  a  disease,  as  the  animal  suffers  no  bad  consequence,  and 
may  even  be  benefited  by  it.^ 

In  still  another  case  (3)  transparent  pelagic  organisms  like 
some  Crustacea  may  appear  phosphorescent  from  containing  in 
their  stomachs  phosphorescent  food,  which  shines  through  the 
body  of  the  organism.  In  a  case  like  this  their  excrement  is 
also  phosphorescent.^ 

1  See  Giard  :  Sur  I'infection  phosphoresc.  des  Talitres  et  autres  crustacees. 
Compt.  Rend.^  Sept.  23,  1889,  p.  503.  Peter  Schmidt :  On  the  Luminosity  of 
Midges  {Chironomus).  Zool.  Jahrb.  Abth.  f.  Syst.  Geog.  tmd  Biologie,  Bd.  VIII, 
Heft  I,  1894.     Ann.  and  Mag  of  Nat.  Hist..,  Vol.  XV,  1895  (translated  by  Austen). 

2  R.  Dubois  :  Sur  le  role  de  la  symbiose  chez  certains  animaux  marins  lumineux 
[Pelagia  et  Pholas].     Cotnpt.  Rend.,  Tome  CVII,  1888,  p.  502. 

3  H.  N.  Moseley:  Notes  of  a  Naturalist,  p.  498. 


114  BIOLOGICAL   LECTURES. 

In  the  truly  phosphorescent  organism  the  luminosity  is 
due  to  the  metabolism  of  the  definite  tissue-cells,  and  the  sub- 
sequent oxidation  of  the  metabolic  product,  which  results  in  the 
emission  of  light. 

There  can  be  no  doubt  that  the  majority  of  luminous 
organisms  belong  to  this  type.  In  some,  certain  cells  of 
the  body  acquire  the  light-producing  property  at  a  certain 
stage  of  development  ;  in  others,  the  organisms  are  luminous 
from  the  beginning  of  their  life  history.  Thus  Alexander 
Agassiz  1  observes  **  that  the  phosphorescence  is  equally  brilliant 
in  the  ^^g  of  Ctenophorae  as  in  the  adults,  even  in  stages  in 
which  the  masses  of  segmentation  can  still  be  counted.  The 
whole  embryonic  mass  becomes  brilliantly  phosphorescent  when 
the  least  shock  is  given  to  the  jar  in  which  the  eggs  are  kept." 

Dubois  ^  also  states  that  in  Lampyris  noctihcca  the  ova  taken 
from  the  ovaries  and  carefully  washed  after  removal  were  still 
luminous,  the  development  of  the  light  being  in  direct  relation 
with  the  degree  of  intraovarian  development  of  the  ova.  The 
photogenic  power  in  such  an  ^^%y  as  in  many  luminous  proto- 
zoa, is  exercised  without  the  aid  of  trachea,  nerves,  or  special 
anatomical  elements,  showing  that  while  these  elements  may 
facilitate  and  even  enhance  for  the  time  being  the  effect  of 
luminosity,  they  are  not  to  be  considered  thereby  essential  to 
the  process  of  light  production. 

Phosphorescence  is  best  seen  in  the  ordinary  fire-fly.  If 
you  examine  the  luminous  cell  of  the  common  fire-fly  {Pho- 
tmis  pennsylvanicd),  you  will  find  it  filled  with  peculiar  yel- 
lowish-white granules,  the  whole  cell  reminding  one  of  some 
actively  secreting  gland.  These  granules,  by  combining  with 
oxygen  brought  in  through  the  trachea  and  tracheal  ''capil- 
laries," which  closely  invest  the  cells  from  all  sides,  give  out 
light.  It  is  a  process  of  combustion  which,  instead  of  giving 
out  heat,  gives  out  light.  These  granules  are  the  products  of 
metabolism,   the  result   of   ''  secretion "   process,   due    to    the 

.  1  A.  Agassiz  :  Embryology  of  the  Ctenophorae.  Mem.  Amer.  Acad,  of  Arts 
and  Sciences,  Vol.  X,  No.  IV.     Cambridge,  Mass.,  1874. 

2  R.  Dubois  :  De  la  fonction  photogenique  dans  les  oeufs  du  lampyre.  Bull. 
Soc.  Zool.  France,  XII,  1887,  p.  137. 


BASIS   OF  ANIMAL   PHOSPHORESCENCE.  II5 

decomposition  of  the  living  substance  of  the  cell ;  but  instead 
of  being  thrown  out  of  the  body,  like  some  other  products  of 
secretion,  they  are  consumed  in  situ  by  combining  with  oxygen 
brought  in  from  without. 

The  fact  that  the  granules  themselves  are  dead  is  shown  by 
taking  the  luminous  organ  from  the  organism  and  crushing  it 
on  the  slide,  thus  depriving  it  of  all  traces  of  vitality  ;  yet  the 
light  continues  to  come  out,  in  fact  it  becomes  more  luminous 
the  greater  the  exposure  to  air. 

The  mode  by  which  each  luminous  cell  is  aerated  by  the 
tracheal  '*  capillaries  "  is  of  considerable  interest.  The  "capil- 
laries" are  the  ultimate  branches  of  the  respiratory  apparatus, 
and  start  from  the  ultimate  branches  of  the  tracheal  tube,  some- 
what in  a  similar  manner  as  the  tentacles  do  from  the  body  of 
a  hydra.  If  one  imagines  these  "  capillaries  "  are  spread  around 
the  photogenic  cell  in  the  same  manner  as  the  hydra  spreads  its 
tentacles  around  an  organism  much  larger  than  itself,  which  it 
has  captured  for  food,  he  may  get  a  fair  idea  of  the  relation  of 
the  aerating  apparatus  to  the  light-producing  cell. 

The  size  of  the  luminous  cell  being  comparatively  large,  more 
than  one  bunch  of  hydriform  "capillaries"  is  found  distributed 
over  the  surface  of  each  luminous  cell.  The  substance  of  the 
"capillaries"  seems  to  have  a  remarkable  affinity  for  oxygen, 
and  it  is,  no  doubt,  through  this  mechanism  that  the  oxygen  of 
the  inspired  air  is  quickly  separated,  and  just  as  quickly  applied 
for  the  combustion  of  the  photogenic  material  in  the  periphery 
of  the  cell. 

As  to  the  chemical  nature  of  this  material  little  is  known  ; 
but  it  is  a  secretion  of  fatty  nature,  which  oxidizes  readily  in 
alkaline  media.  Phosphorus  has  nothing  to  do  with  the 
phenomenon. 

The  animal  has  control  of  the  production  of  light  through 
its  respiratory  mechanism,  not  directly  upon  the  luminous 
cell,  although  nerves  may  have  indirect  influence  upon  the 
general  metabolism  of  the  cell.  When  more  oxygen  is  sent 
with  the  air,  the  illumination  is  greater ;  when  the  air  is  with- 
held, there  is  less  light,  or  even  a  complete  darkness,  just  as  the 
dull  red  coal  may  be  ignited  so  as  to  emit  a  white  light  by  a 


Il6  BIOLOGICAL   LECTURES. 

Steady  application  of  fresh  air  upon  it  by  the  action  of  the 
bellows. 

The  fact  that  the  illumination  of  the  cell  is  due  to  the  action 
of  oxygen  may.  be  shown  in  a  simple  way  by  putting  the  slide 
on  which  the  luminous  organ  has  been  crushed,  and  the  photo- 
genic material  spread  out,  into  a  jar  containing  carbon  dioxide. 
The  light  disappears  almost  instantly;  but  if  the  same  slide  be 
placed  in  a  jar  containing  oxygen,  or  simply  exposed  to  air,  the 
light  comes  back,  and  lasts  as  long  as  the  luminous  material, 
a  certain  amount  of  moisture,  and  other  necessary  conditions 
are  present. 

This  process  can  be  repeated  several  times,  showing  conclu- 
sively that  the  light-giving  material  itself  is  quite  independent 
of  cell-life,  although  it  owes  its  existence  primarily  to  the  life 
activity  of  the  cell  as  a  whole. 

The  luminous  phenomenon,  wherever  it  occurs,  is  apparently 
carried  on  by  essentially  the  same  process  throughout  the 
animal  kingdom.  In  air-breathing  organisms,  such  as  the 
fire-fly,  the  product  of  cell  metabolism  is  oxidized  in  sitti  by 
the  oxygen  of  the  inspired  air.  In  some  marine  organisms  the 
secretion  is  often  thrown  out  in  the  form  of  liquid  from  the 
gland  to  the  surrounding  medium,  and  the  oxidation  is  accom- 
plished by  the  oxygen  dissolved  in  the  sea  water.  In  luminous 
Salpa  the  photogenic  granules  formed  in  the  blood-corpuscles 
are  oxidized  by  the  oxygen  dissolved  in  the  blood  plasma. 

Perhaps  I  can  summarize  the  preceding,  and  make  my  point 
more  intelligible  by  the  help  of  a  diagram. 

We  have  seen  that  the  essential  bases  for  the  luminous 
phenomena  of  the  living  organism  consist  (i)  in  the  production 
of  a  certain  chemical  substance  in  the  cell,  which  recalls  to  our 
mind  the  well-known  series  of  phenomena  in  the  process  of 
secretion ;  and  (2)  the  oxidation  of  this  substance  by  the 
oxygen  brought  in  from  without,  and  thus  making  the  cell  a 
new  center  of  disturbance  to  the  surrounding  ether. 


BASIS   OF  ANIMAL   PHOSPHORESCENCE. 

M 


117 


Living  Constituents  of  the  Cell. 


M  Protoplasm 


( (a)  Cytoplasm. 


NoN-LiviNG  Constituents  of  the  Cell. 

(a)  Food  {A). 

(b)  Photogenic  granules  (Z). 


I  (b)  Chromosome. 
O  Oxygen,  acting  on  the  photogenic 

granules. 
Z  Light,  emanating  from  the  cell,  as 

the  result  of  oxidation. 

The  food-substance,  which  I  represent,  for  the  sake  of  con- 
venience, by  the  block  {A)  in  the  accompanying  diagram,  enters 
the  cell  boundary,  and  becomes  eventually  assimilated  into  the 
protoplasm  (M) ;  the  complex  living  substance,  or  protoplasm, 
becomes  disintegrated  into  a  number  of  granules  {Z)  which 
are  no  longer  ''living,"  and  which  may  be  regarded  as  refuse 
of  life.  The  definite  chemical  molecules  which  constitute 
these  granules  combine  with  oxygen  (0,  and  the  molecular 
agitation,  which  accompanies  the  chemical  process  of  combus- 
tion, sets  the  surrounding  ether  into  a  state  of  vibration  (Z), 
which  has  a  powerful  luminous  effect  on  us,  but  little  or  no 
thermal  effect. 

Thus,  the  life  of  the  luminous  cell,  like  that  of  any  other 
cell,  begins  with  the  physical  and  ends  with  the  physical.  We 
know  the  beginning  {A)\  and  we  also  know  the  termination  (Z). 
The  unknown  territory  in  the  middle  {M)  is  what  we  call  the 
protoplasm,  or  the  matter  in  the  living  state. 


Il8  BIOLOGICAL   LECTURES. 

There  is  one  suggestion  of  some  importance  which  flows 
from  this. 

That  most  Hving  matter  needs  oxygen  for  the  maintenance 
of  life  is  a  well-established  fact,  but  in  what  precise  manner 
this  oxygen  is  ultimately  used  in  the  organism,  is  a  question  to 
which  we  can  give  hardly  any  satisfactory  answer  at  present. 

In  the  luminous  cell  of  the  fire-fly,  in  which  the  mechanism 
of  oxygenation  is  carried  to  its  highest  perfection,  it  is  com- 
paratively easy  to  trace  the  path  of  oxygen,  and  how  it  is  used 
in  the  living  cell.  TJie  oxygen  here  simply  combines  with  tJie 
dead  substance  prepared  in  the  cell.  The  value  of  oxygen  to  the 
luminous  function  of  the  organism  lies  in  its  ability  to  combine 
with  the  dead  substance  produced  by  the  activity  of  the  living. 
Is  it  possible  that  the  relation  of  oxygen  to  life  in  general  is  of 
a  similar  nature  }  Does  the  value  of  oxygen  to  life  lie  primarily 
in  its  ability  to  combine  with  the  dead  substances,  which  exist 
side  by  side  with  the  living,  in  all  cells }  The  haemoglobin  is 
a  complex  iron  compound  found  in  the  red  blood-corpuscle. 
Oxygen  loosely  combines  with  this  compound  and  forms  oxy- 
haemoglobin.  The  oxygen  in  this  new  compound  is  given  up 
in  the  tissue  through  which  the  blood  circulates,  and  the  com- 
pound returns  back  to  the  original  haemoglobin,  which,  coming 
back  to  the  respiratory  organ,  combines  again  with  the  free  oxy- 
gen, and  begins  the  role  of  oxygen-carrier  again.  Here,  again, 
the  substance  in  the  cell  which  combines  with  the  oxygen  is  not 
the  living  substance,  but  the  dead  material  formed  by  the  activity 
of  the  cell.  Professor  Loeb  suggests  that  it  is  possible  that 
the  relation  of  oxygen  to  life  may  be  of  this  nature  in  all  cases. 

It  may  be  that  in  the  luminous  cell  of  the  fire-fly  the  method 
of  oxidation  is  carried  out  with  a  highly  specialized  apparatus, 
and  the  result  of  oxidation  of  the  dead  material  conveyed  in 
such  a  form  as  to  affect  the  most  delicate  of  our  sense-organs, 
and  that  the  relation  of  oxygen  to  the  life  of  the  cell  in  gen- 
eral is  thus  revealed  here  with  simplicity  and  clearness  unparal- 
leled in  the  whole  series  of  vital  activities.  At  any  rate,  this 
aspect  of  the  question  may  not  be  devoid  of  interest  when  taken 
in  connection  with  the  fundamental  problem  of  the  relation  of 
oxygen  to  living  substance,  or  respiration,  in  which,  some  have 
even  maintained,  lies  hidden  the  whole  mystery  of  life. 


EIGHTH    LECTURE. 


THE  PRIMARY  SEGMENTATION  OF   THE  VERTE- 
BRATE   HEAD. 

WILLIAM   A.    LOCY. 

(Lake  Forest,  III.) 

The  vertebrate  head  is  the  most  complex  piece  of  animal 
architecture  with  which  anatomists  have  to  deal.  It  has  been 
produced  by  gradual  modifications  of  a  simpler  basis,  and  dif- 
ferentiation has  been  carried  farther  in  it  than  in  any  other 
part  of  the  animal.  It  represents,  therefore,  the  widest  depar- 
ture from  archetypal  conditions. 

Its  complex  structure  is  correlated  with  the  highest  grade  of 
functions.  The  cranial  sense-organs  and  the  brain  exhibit 
the  highest  manifestations  of  vital  activity  to  be  found  in  the 
whole  range  of  living  structures.  The  cranial  sense-organs 
serve  to  bring  the  organism  into  relation  with  the  external 
world,  and  the  brain,  besides  being  concerned  with  perception 
and  general  mental  life,  contains  nerve-centers  for  the  coordina- 
tion of  the  vital  actions  of  the  body.  The  structure  and  de- 
velopment of  the  vertebrate  head  is  therefore  a  topic  of  unusual 
interest  and  importance  in  comparative  anatomy. 

In  their  efforts  to  understand  the  head,  morphologists 
and  physiologists  have  made  use  of  every  available  means  of 
research ;  observations  on  the  minute  structure  have  been 
supplemented  by  studies  in  embryological  development  and 
physiological  experimentation.  The  whole  work  has  been 
carried  on  from  the  standpoint  of  comparative  anatomy.  The 
results  have  not  been  just  what  might  have  been  expected 
They  have  not  led  to  the  solution  of  the  fundamental  questions, 
but  have  served  rather  to  open  the  field  and  reveal  its  extent 


I20  BIOLOGICAL   LECTURES. 

and  complicated  nature.  A  research  once  begun  leads  out  in 
all  directions  into  the  unknown,  and  a  crop  of  new  problems 
springs  up  in  the  path  of  the  original  investigator.  It  is  en- 
couraging to  biologists  to  know  that  every  research  serves 
to  enlarge  the  field  of  their  activity ;  the  conquered  territory 
affords  points  of  vantage  from  which  the  horizon  is  enlarged. 
Thus  the  work  of  morphologists  and  physiologists  on  the 
head,  although  not  giving  a  complete  solution  to  the  problems 
undertaken,  has  brought  us  larger  views  and  more  interesting 
and  suggestive  lines  of  inquiry. 

Out  of  the  great  group  of  subjects  connected  with  the 
morphology  of  the  head,  I  have  chosen  one  that  relates  to  the 
primitive  segmented  condition.  If  we  propound  the  question, 
What  was  the  rudimentary  condition  of  the  vertebrate  head.? 
we  shall  find  it  may  be  partly  answered  in  the  light  of  modern 
research  as  follows :  It  was  originally  composed  of  a  series  of 
similar  segments  that  were  structurally  like  those  that  compose 
the  trunk.  A  mental  picture  of  this  rudimentary  condition 
may  be  formed  by  thinking  of  the  broad  cephalic  plate  (or 
rudimentary  head)  of  very  early  embryonic  stages  as  divided 
by  transverse  constrictions  into  ridges  and  furrows  that  pass 
backward  from  the  head  into  the  trunk,  and  give  the  whole 
embryo  a  jointed  structure  similar  to  that  of  an  articulated 
animal.  The  segments  or  folds  do  not  cross  the  median  plane, 
and  are  therefore  in  pairs.  From  this  simple  condition  the 
complex  head  has  arisen  by  differentiation  and  specialization. 
It  follows,  of  course,  that  the  distinction  between  head-region 
and  trunk-region  is  one  of  degree  of  differentiation  and  not  of 
kind. 

The  head  is  least  modified  in  the  youngest  embryos,  and  if 
we  begin  our  observations  with  the  earliest  stages  its  trans- 
formations may  be  traced  by  observing  successively  older 
embryos.  The  modifications  which  the  head  has  undergone 
have  been  brought  about  gradually,  and  are  so  comprehensive 
in  their  range  that  if  we  could  know  their  complete  history, 
even  in  one  animal,  we  should  have  a  key  to  the  leading  ques- 
tions of  vertebrate  descent.  But  there  are  so  many  causes 
tending  to  modify  the  course  of  development,  that  we  cannot 


THE  PRIMARY  SEGMENTATION.  121 

depend  on  the  steps  of  ancestral  history  being  repeated  in  a 
complete  and  orderly  way  in  any  animal  form,  and  our  observa- 
tions give  us  only  circumstantial  evidence  from  which  a  balance 
of  probabilities  must  be  struck  to  determine  what  is  ancestral 
and  what  is  secondarily  acquired.  The  chain  of  evidence  is 
incomplete,  and  must  always  be  supplemented  by  a  certain 
amount  of  inference,  but  it  has  not  been  fully  recognized  in 
the  practical  study  of  embryological  development  that  the 
shortest  intervals  of  time  may  be  very  important  in  keeping 
the  connection.  Coherency  of  history  must  be  preserved. 
The  difficulty  of  doing  so  is  greatly  increased  by  the  fact  that 
the  new  is  made  to  proceed  out  of  the  old,  and  frequently  one 
organ  insidiously  takes  the  place  of  an  earlier  formed  one.  I 
am  glad  of  the  opportunity  to  say,  in  this  company  of  investi- 
gators and  students  who  are  preparing  for  independent  research 
in  biology,  that  too  great  stress  cannot  be  laid  on  the  desir- 
ability of  having  a  more  complete  series  of  stages  for  study. 
The  traditional  method  has  been  to  study  one  stage,  and  then 
another  '*a  little  older,"  and  fill  in  the  gap  with  inferences. 
This  has  proved  to  be  inadequate  and  misleading.  It  is  now 
required  that  we  shall  have  stages  near  enough  to  trace  the 
history  of  the  transitory  as  well  as  the  permanent  organs ; 
embryologists  are  just  beginning  to  realize  how  transitory 
some  organs  are.  I  have  recently  had  occasion  to  examine  a 
set  of  embryonic  structures  in  the  chick,  which  do  not  appar- 
ently last  more  than  an  hour  or  two  in  the  course  of  develop- 
ment, but  which  are,  nevertheless,  clearly  defined  for  that 
period  and  then  fade  away.  In  this  particular  case  the  agree- 
ment of  two  observers,  even  as  to  the  presence  of  these  organs, 
would  depend  on  their  having  stages  of  identically,  not  approxi- 
mately, the  same  period  of  development.  A  wider  recognition 
of  the  existence  of  such  conditions  would  give  us  fewer  contro- 
versies and  less  biological  mythology. 

Above,  it  was  stated  that  the  vertebrate  head  is  primitively 
segmented,  and  it  is  manifestly  an  interesting  problem  to  deter- 
mine the  number,  the  nature,  and  the  transformations  of  the 
segments  that  have  entered  into  the  composition  of  the  head. 
The  individual  segments  are  called  metameres,  or  somites,  and 


122  BIOLOGICAL   LECTURES. 

the  jointed  condition  is  designated  "metamerism  of  the  head." 
Under  that  title  the  question  has  recently  received  much  atten- 
tion. It  is  not  a  new  question,  having  been  started  at  the 
beginning  of  this  century,  but  there  has  been  a  revived  interest 
in  it  on  account  of  new  discoveries.  It  was  the  most  promi- 
nently discussed  question  before  the  Anatomical  Society  of 
Germany,  at  their  meeting  in  Vienna,  in  1892.  There  were 
important  papers  on  the  subject  by  some  of  the  foremost 
anatomists,  —  Froriep,  Kupffer,  Hatscheck,  Rabl,  Killian, — all 
followed  by  discussion,  and  the  question  of  metamerism  of  the 
head  received  there  a  consideration  worthy  of  its  importance. 
There  have  been  new  developments  since  that  time,  tending  to 
modify  some  of  the  conclusions  reached  in  that  learned  body, 
and  the  subject  is,  on  account  of  its  freshness,  a  particularly 
good  one  to  present  here. 

The  presence  in  the  head  of  such  segmental  structures  as 
cranial  nerves,  branchial  clefts,  of  the  adult  and  embryonic 
stages,  the  so-called  head  cavities  and  neural  segments,  have 
been  sufficient  evidence  to  support  the  general  proposition  that 
the  vertebrate  head  is  segmented  in  its  unmodified  condition. 
But  there  has  been  no  agreement  as  to  the  number,  nature, 
or  transformations  of  these  segments,  nor  as  to  their  anterior 
limit.  In  fact,  the  fore-brain  has  generally  been  regarded  as 
not  included  in  the  segmented  area. 

Segmental  folds  have  been  observed  in  the  hind-brain  of 
embryos  of  different  animals  since  1828,  so  there  has  been  no 
question  as  to  the  segmented  condition  of  the  posterior  part  of 
the  brain,  but,  so  far  as  the  evidence  (except  the  very  latest) 
goes,  the  segments  seem  to  vanish  in  the  region  of  the  fore- 
brain,  and  the  general  interpretation  has  been  that  the  fore- 
brain  is  non-metameric.  The  two  anterior  pairs  of  nerves  com- 
ing from  the  fore-brain  —  olfactory  and  optic — have  also  until 
very  recently  been  placed,  by  common  consent,  in  a  different 
category  from  the  other  cranial  nerves.  Moreover,  the  head  has 
been  considered,  by  some  of  the  most  careful  students  of  our 
time,  to  be  derived  from  an  unsegmented  ancestral  rudiment 
found  in  an  enigmatical  larval  form  of  the  annelids.  All  this 
gave  rise  to  the  assumption  that  the  brain  of  invertebrates  and 


THE   PRIMARY  SEGMENTATION.  123 

vertebrates  contained  an  unsegmented  anterior  part,  and  the 
question,  How  far  forward  does  the  segmentation  extend  ? 
is  a  very  important  one. 

The  evidence  to  elucidate  this  point  has  been  accumulating, 
and  I  think  we  are  now  in  a  position  to  answer  that  fundamen- 
tal question.  Already  the  olfactory  nerves  have  been  shown 
to  have  a  similar  history  to  the  cranial  nerves,  and,  to  all 
appearances,  the  optic  nerves  are  soon  to  be  included  with  the 
others.  The  Director  of  this  laboratory  has  recently  shown 
conclusively  that  the  head  of  annelids  is  metameric  throughout. 
The  cerebral  ganglion  or  brain  of  these  animals  is  segmented 
in  the  same  manner  as  the  ventral  nerve-cord,  and  consequently 
there  is  no  non-metameric  part  of  the  nervous  system,  as  has 
been  so  long  assumed.  This  must  necessarily  change  the  views 
regarding  the  ancestral  derivation  of  the  vertebrate  head. 
Waters,  Zimmerman,  and  others  have  shown  the  existence  of 
segments  in  the  fore-brain  of  vertebrates,  and  further  evidence 
on  that  point  will  be  brought  out  in  this  lecture. 

The  recent  endeavors  to  solve  the  problem  of  metamerism 
of  the  head  are  based  on  observations  on  cranial  nerves  and 
branchial  clefts,  mesoblastic  head  cavities  and  neural  segments. 
These  are  the  cephalic  structures  that  exhibit  segmental  ar- 
rangement, and  we  must  depend  upon  them  for  evidence.  It 
is  an  open  question  to  which  of  these  the  most  importance  is 
to  be  attached.  The  first-mentioned  basis,  namely,  cranial 
nerves  and  branchial  clefts,  is  the  least  favorable,  as  it  involves 
too  much  conjecture.  Dr.  Strong,  of  Columbia  University,  has 
shown  that  the  cranial  nerves  do  not  appear  in  the  positions 
they  come  to  occupy,  and  McClure  has  stated  the  case  against 
the  cranial  nerves  as  follows  :  **We  have  positive  proof  that 
the  degeneration  of  certain  branches  has  taken  place.  This 
being  the  case,  we  have  every  reason  to  assume  that  whole 
segmental  nerves  may  have  once  existed,  which  have  completely 
degenerated,  leaving  no  trace  whatever  of  their  previous  exist- 
ence. If  such  be  the  case,  the  segments  originally  connected 
with  these  degenerated  nerves  must  necessarily  be  overlooked, 
if  the  existing  nerves  are  made  use  of  as  a  means  of  determin- 
ing the  original  number  of  segments. 


124  BIOLOGICAL   LECTURES. 

"■  Furthermore,  the  vagrant  changes  in  the  position  of  some 
of  the  cranial  nerves  must  necessarily  cause  confusion.  For 
example,  take  the  sixth  nerve,  which  in  the  frog  and  tadpole 
stages  is  situated  between  the  first  and  second  roots  of  the 
ninth  nerve  (given  on  the  authority  of  Dr.  Strong),  a  position 
somewhat  posterior  to  its  place  of  origin.  This  remarkable 
shifting  clearly  shows  not  only  what  great  changes  in  position 
the  cranial  nerves  are  capable  of  undergoing,  but  it  also  goes 
to  prove  that  we  can  find  no  reliable  means  of  determining  the 
primitive  segments  by  means  of  their  connection  with  the  exit 
of  the  existing  cranial  nerves.  Beard,  in  taking  up  this  problem, 
made  use  of  an  important  series  of  sense-organs  for  which  he 
proposed  the  name  '  branchial  sense-organs,'  from  their  de- 
velopment from  thickenings  of  the  epiblast  over  each  branchial 
cleft.  The  dorsal  branches  of  certain  cranial  nerves  fuse  with 
these  epiblastic  thickenings ;  the  superficial  part  of  the  thicken- 
ing gives  rise  to  a  branchial  sense-organ,  while  the  deeper  por- 
tion becomes  the  ganglion  of  the  dorsal  root  of  the  cranial 
nerve.  This  close  relation  which  exists  between  the  dorsal 
branches  of  the  cranial  nerves  and  their  corresponding  sense- 
organs  is  undoubtedly  of  segmental  character.  But  this  line  of 
research  is  beset  by  a  great  difficulty,  namely,  that  the  degen- 
eration of  certain  sense-organs  would,  in  time,  involve  the 
degeneration  of  their  corresponding  cranial  nerves,  and  such 
degeneration  has  taken  place,  in  part  or  in  whole,  leaving  in 
doubt  the  primitive  segments  with  which  they  were  connected." 

The  mesoblastic  head-cavities  and  neural  segments  are  both 
more  important  clues  to  the  metamerism  of  the  head.  The 
mesoblastic  head-cavities  are  called  myotomes,  and  embody 
the  muscle  rudiments,  while  the  neural  segments  represent  the 
joints  of  the  nervous  system.  Muscle  and  nerve  are,  physio- 
logically, so  fundamentally  related  that  we  should  naturally  ex- 
pect some  close  correspondence  between  muscle  segments  and 
neural  segments,  and  metamerism  of  the  head  should  be  studied 
in  the  light  of  observations  on  both  sets  of  structures. 

Balfour  first  studied  the  segmental  divisions  of  the  meso- 
blast  in  the  head  of  elasmobranch  fishes,  and,  in  1874,  identi- 
fied by  this  means  eight  head  somites.     He  also  expressed  the 


THE  PRIMA  R  Y  SEGMENT  A  TION.  \  2  5 

conviction  that  there  were  primitively  a  larger  number  of  seg- 
ments, but,  owing  to  extreme  modifications  of  the  head-region, 
they  are  no  longer  clearly  represented. 

From  this  time  onwards,  the  myotomes  became  a  great 
favorite  with  morphologists  in  elucidating  the  problem  of  head 
segmentation.  They  seemed,  so  far  as  the  evidence  went,  to 
embody  the  most  direct  survivals  of  the  original  segmentation, 
and  therefore  to  be  the  most  promising  line  along  which  to 
work  out  the  problem.  Van  Wijhe's  researches,  published 
about  1882,  have  been  taken  as  the  standard  ones  for  reference  ; 
he  identified  nine  head  somites  moulded  in  the  mesoblast  of  the 
head.  This  line  of  investigation  received  a  great  stimulus  in 
1890,  from  the  work  of  Dohrn,  who  discovered  eighteen  or 
nineteen  myotomes  in  the  head  of  torpedo  embryos.  In  1892 
Killian  substantiated  his  discoveries  and  reduced  the  enumer- 
ation by  one.  It  appears,  therefore,  that  there  is  a  larger 
number  of  head  somites  than  was  at  first  supposed. 

The  neural  segments  are  comparatively  recent  in  their  claims 
to  attention  as  bearing  evidence  to  the  original  segmentation 
of  the  head,  and  their  importance  in  this  connection  has  not 
been  fully  appreciated.  Their  early  history  has  recently  been 
made  known,  ^  and  this  shows  them  in  a  new  light.  The  neural 
segments  are  the  first  to  appear,  and  are  less  subject  to  modi- 
fications in  the  early  stages  than  the  muscle  segments  of  the 
head.  The  large  number  of  myotomes  described  by  Dohrn 
and  Killian  are  transitory,  and  after  a  very  brief  existence  they 
become  reduced  by  fusion,  or  absorption,  or  both,  to  the  nine 
head-cavities  of  Van  Wijhe.  But  the  neural  segments  make 
their  appearance  very  early  and  preserve  their  original  number 
and  characteristics  for  a  considerably  longer  period.  It  has 
been  assumed  that  the  muscle  segments  are  primary  and  that 
the  neural  segments  are  secondarily  moulded  over  them  ;  but,  as 
we  shall  see,  this  position  cannot  be  sustained  in  the  light  of 
recent  observations,  and  it  is  timely  to  ask  which  set  of  seg- 
mental structures  affords  the  most  reliable  evidence  as  to  the 
primitive  number  of  brain  segments. 

1  Locy  :  Metameric  Segmentation  in  Medullary  Folds  and  Embryonic  Rim. 
Anat.  Anz.,  Bd.  IX,  No.  13,  1894  ;  2i\so  Journ.  Morph.,  Vol.  XI,  No.  3. 


126  BIOLOGICAL   LECTURES. 

I  have  said  that  the  metamerism  of  the  head  should  be  in- 
vestigated in  the  light  of  work  done  on  both  myotomes  and 
neural  segments,  but  here  I  can  present  only  one  side.  The 
case  for  the  myotomes  has  been  so  completely  presented  by 
Dohrn,  Killian,  and  others  that  I  waive  a  consideration  of  that 
side  of  the  question,  and  dwell  on  the  history  of  the  neural  seg- 
ments and  speak  of  the  new  observations  on  them. 

The  neural  segments  were  observed  in  the  hind-brain  of 
embryo  chicks  by  Von  Baer  as  long  ago  as  1828.  They  have 
been  observed  and  commented  upon  by  many  anatomists  since 
that  time.  In  1850  Dursy  made  the  important  suggestion 
that  the  neural  segments  are  genetically  related  to  the  cranial 
nerves,  but  he  had  no  direct  evidence  of  this.  To  Beraneck 
belongs  the  credit  of  having  first  demonstrated,  in  1884,  that 
there  is  a  definite  relation  between  neural  segments  and  certain 
cranial  nerves.  This  was  the  first  substantial  basis  towards 
establishing  their  segmental  importance.  Orr,  'Zj,  McClure, 
'90,  and  Waters,  '92,  followed  this  pioneer  work,  demonstrating 
the  definite  relation^  of  the  nerves  of  the  hind-brain  to  specific 
neuromeres.  McClure  showed  also  that  the  entire  neural  tube 
is  divided  into  similar  segments,  and  Waters  gave  particular 
attention  to  the  fore-  and  mid-brain.  He  found  in  the  lizard 
evidence  of  three  somites  in  the  fore-brain,  making  a  total  of 
eleven  somites  in  the  entire  brain-region. 

In  Europe  Froriep,  Kupffer,  Rabl,  Hoffmann,  Zimmerman, 
and  others  have  made  recent  contributions  to  the  knowledge 
of  these  neural  segments.  In  1892  Froriep  described  anew 
the  neural  segments  and  attached  no  particular  importance  to 
them.  He  expressed  the  conclusion  that  the  neural  segments 
are  secondarily  moulded  over  the  segmental  divisions  of  the 
mesoblast.  The  latter,  in  common  with  most  other  writers,  he 
regards  as  primary.  I  hope  to  show  you  before  the  conclusion 
of  this  lecture  that  the  position  cannot  be  sustained. 

Let  us  now  see  what  may  be  learned  regarding  the  primitive 
segments  of  the  head  by  the  examination  of  young  embryos. 

1 1  prefer  to  omit  in  this  general  lecture  the  question  of  the  relationship  of  par- 
ticular cranial  nerves  to  particular  neural  segments,  which  is  of  so  great  interest 
and  importance  to  the  morphologist. 


THE  PRIMARY  SEGMENTATION. 


127 


In  choosing  an  advantageous  animal  for  observation,  we  should 
take  a  vertebrate  that  has  undergone  relatively  few  modifica- 
tions. Of  course,  any  living  animal  is  very  far  removed  from 
the  ancestral  type,  but  we  should  expect  to  find  the  closest 
approach  to  ancestral  conditions  in  the  simplest  ones.  The 
sharks  present  many  generalized  features  and  we  may  as  well 
begin  with  them. 

It  is  to  be  understood  that  I  am  responsible  for  the  observa- 
tions that  follow,  as  they  have  not,  as  yet,  been  substantiated 
by  any  other  observer.  The  careful  examination  of  an  elasmo- 
branch  embryo  in  an  early  stage  of  development  shows  the 
existence   of   segmental   folds  that  extend  from  the  extreme 


Fig.  I.  — Very  young  embryo  of  Acanthias  showing  primitive  segments. 

anterior  end  to  the  posterior  limit  of  the  embryo.  Fig.  i 
represents  such  an  embryo.  The  specimen  from  which  the 
sketch  was  made  had  attained  a  length  of  i.i  mm.  The 
axial  part  of  the  embryo  is  established  ;  its  anterior  end  is 
rounded  and  slightly  broader  than  the  rest  of  the  embryo. 
There  are  eight  pairs  of  segments  in  the  axial  embryo,  and 
they  extend  beyond  into  the  blastodermic  rim.  If  these  seg- 
mental folds  occurred  only  in  isolated  cases,  or  in  a  single 
embryonic  stage,  we  should  attach  no  especial  significance  to 
them,  but  they  are  present  in  all  normal  specimens,  and  their 
history  shows  their  segmental  importance.  Once  established, 
they  may  be  traced  onwards  in  unbroken  continuity  and  finally 
identified  with  the  neuromeres  described  by  Orr,  McClure,  and 
others.  There  are  three  or  four  pairs  of  mesoblastic  divisions 
in  this  stage  that  occupy  a  limited  area  in  the  narrow  part  of 


128  BIOLOGICAL   LECTURES. 

the  embryo,  but  the  segmental  folds  are  comprehensive  in  ex- 
tent and  cannot  depend  on  these  few  proto vertebrae. 

The  examination  of  a  slightly  older  embryo,  Fig.  2,  gives  a 


Fig.  2. — Young  embryo  of  Acanthias  showing  primitive  segments.    Those  numbered  i-ii  lie  in 
front  of  the  point  of  origin  of  the  vagus  nerve. 

similar  picture.  The  segments  are  a  little  better  developed, 
and  the  broad  head-region  is  roughly  marked  off  from  the  more 
slender  trunk-region.  The  segments  extend  along  the  margin 
in  pairs.  As  in  the  former  case,  they  extend  beyond  the  limit 
of  the  axial  embryo  into  the  embryonic  rim.  There  are  eleven 
pairs  in  the  broadly  expanded  head  end.  It  may  be  determined 
by  tracing  them  into  later  stages  that  the  eleventh  neuromere 
is  just  in  front  of  the  place  of  origin  of  the  front  root  of  the 
vagus  nerve. 

It  is  obvious  that  this  young  animal  that  is  to  be  hatched 
from  the  ^g^  as  a  vertebrate  is  now  an  invertebrate.  It  ex- 
hibits an  arthromeric  condition  similar  to  that  in  animals  of  the 
articulated  group.  The  segments,  although  faintly  expressed, 
are  definite  in  number  and  arrangement,  and  the  inference  to 
be  drawn  from  their  presence  is  clear.  As  Dr.  Whitman  has 
said :  "  This  is  a  stage  through  which  every  vertebrate  passes 
on  its  way  from  the  ^gg  to  the  adult,  a  stage  in  which  the  fish, 
the  amphibian,  the  reptile,  the  bird,  the  beast,  and  man  find 
a  common  level,  and  in  which  every  title  to  superior  rank 
lies  in  unexpressed  potentialities.  But  more  than  this ;  for 
it  is  here  that  the  vertebrate  is  an  invertebrate  and  stands 
beside   its  prototype,  the  segmented   worm.       On    the   same 


THE  PRIMARY  SEGMENTATION, 


129 


metropolitan  plane  the  lobster,  the  crab,  the  insect,  in  short 
all  the  members  of  the  great  arthropod  group,  meet  and 
acknowledge  their  community  of  descent.  Thus  the  great 
branches  of  the  genealogical  tree  represented  in  the  larger 
types  first  defined  by  Cuvier  converge  and  meet  in  a  common 
trunk  which  bears  the  deep  and  enduring  mark  of  metamerism." 


Fig.  3.  —  Older  embryo  showing  metameric  segments  in  the  head-plate.    The  neural  folds  of  the  head 
are  nearly  in  the  horizontal  plane,     op,  beginning  of  the  optic  vesicle. 

Fig.  3  shows  an  older  embryo  with  a  slender  trunk  and 
broadly  expanded  head.  The  optic  vesicles  {op)  have  made 
their  appearance  on  the  head-plate.  The  neural  segments  are 
well  shown  on  the  left-hand  margin  of  the  cephalic  plate. 

Fig.  4  shows  a  still  older  embryo  in  which  the  neural  folds 
of  the  head  have  grown  upwards  to  form  an  open  neural  groove. 


Fig.  4.  —  Embryo  with  open  neural  groove, 
vesicle,     he,  head-cavity. 


1-13  metameres  of  the  neural  folds.    oP,  primary  optic 


130  BIOLOGICAL   LECTURES. 

The  embryo  is  viewed  obliquely  from  the  right  side.  The  rudi- 
ments of  several  organs  —  optic  vesicles,  branchial  pouch,  etc. 
—  have  appeared  upon  the  lateral  walls  of  the  head.  Direct- 
ing our  attention  to  the  margin  of  the  nearest  neural  fold,  we 
note  that  it  is  clearly  segmented  throughout  the  head-region, 
and  backwards  into  the  trunk  to  the  point  where,  in  the  figure, 
it  disappears  behind  the  yolk.  The  metameres  extend,  in 
reality,  to  the  posterior  limit  of  the  body. 

The  next  stage  to  be  considered.  Fig.  5,  is  immediately  after 

^^    <^    /^      /-o     « 


jf 


'op 

Fig.  5.  —  Head  of  embryo  of  Acanthias  after  closure  of  the  neural  groove  but  before  the  formation 
of  the  auditory  vesicle.     Reference  marks  as  in  the  previous  figure. 

the  closure  of  the  neural  groove  and  before  the  auditory  vesicle 
has  made  its  appearance.  Certain  anatomical  landmarks  of  the 
head-region  have  become  established,  and  it  is  now  possible  to 
determine  the  relation  of  the  neural  segments  to  other  cephalic 
structures. 

It  is  to  be  noted  that  the  metameres  of  the  fore-  and  mid- 
brain are  still  visible  from  surface  views,  and  almost  immedi- 
ately become  indistinguishable  in  these  regions,  but  continue 
to  be  well  defined  in  the  hind-brain.  There  are  five  segments 
well  shown  in  the  combined  fore-  and  mid-brains.  Three  of 
these  probably  belong  to  the  fore-brain  and  two  to  the  mid- 
brain. All  the  embryos  so  far  described  exhibit  the  segmental 
folds  to  the  anterior  end  of  the  head,  and  a  definite  answer  is 
returned  by  these  observations  to  the  fundamental  question 
already  proposed  :  How  far  forward  does  the  segmentation 
extend.?     In  view  of  the  facts,  we  are  justified  in  concluding 


THE   PRIMARY  SEGMENTATION. 


131 


that  the  extreme  anterior  end  of  the  vertebrate  brain  still  bears 
the  marks  of  primitive  segmentation.  This,  as  Dr.  Whitman 
has  shown,  is  also  the  case  with  the  invertebrates. 

In  Fig.  6,  the  auditory  vesicle  is  formed.     The  neural  seg- 
ments of  the  fore-  and  mid-brains  are  no  longer    discernible 


'mb 


Fig.  6.  —  Head  of  embryo  after  the  formation  of  the  auditory  vesicle,  the  first  five  head  segments  no 
longer  distinguishable,     au,  auditory  vesicle,     na,  nasal  epithelium,     tnb,  mid-brain. 

from  surface  view,  but  those  of  the  hind-brain,  beginning  with 
No.  6,  are  clearly  seen.  The  neuromeres  of  that  region  are 
now  in  contact  in  the  median  plane  ;  soon,  by  the  lateral  growth 
of  the  upper  brain  wall,  they  become  separated  as  shown  in  Fig. 
7.  This  is  the  stage  in  which  neural  segments  have  been  here- 
tofore described.    They  have  been  designated  neuromeres.   The 


Fig.  7.  —  Head  of  embryo  somewhat  older  than  the  one  in  Fig.  6. 
Other  reference  marks  as  before. 


nv,  beginning  of  the  fifth  nerve. 


132 


BIOLOGICAL   LECTURES. 


cranial  nerves  have  begun  to  develop  and  show  definite  relations 
with  some  of  the  neuromeres  of  the  hind-brain.  For  example, 
as  is  best  shown  in  Fig.  7,  the  fifth  nerve  is  connected  with  the 
first  and  second  neuromeres  of  the  hind-brain,  that  is,  with  the 
segments  Nos.  6  and  7.  The  eighth  neuromere  has  no  nerve 
connection ;  the  seventh  and  eighth 
nerves  are  connected  with  the  ninth 
and  tenth  neuromeres  ;  the  ninth  nerve 
with  the  eleventh  neuromere,  and  the 
front  root  of  the  vagus  is  connected 
with  the  twelfth  segment. 

The  evidence  of  a  primitive  head 
segmentation,  which  is  so  well  preserved 
in  these  animals,  is  by  no  means  ex- 
ceptional, as  may  be  determined  by 
examining  the  embryos  of  other  animals. 
They  are  present  at  least  in  corre- 
spondingly young  stages  of  birds  and 
amphibia,  and  this  considerable  range 
indicates  they  are  a  fundamental  char- 
acteristic. 

In  the  very  young  chick,  I  have 
repeatedly  examined  them  in  living 
specimens.  They  are  to  be  faintly 
seen  as  early  as  the  twelfth  to  the 
fifteenth  hour  of  incubation  ;  and  from 
that  time  onwards  they  are  ever  present 
till  they  are  obliterated  by  transforma- 
tions in  the  brain.  In  the  earlier 
stages  in  which  I  have  observed  them 
there  are  only  three  pairs,  and  they 
apparently  increase  in  number  by  backward  growth.  Fig.  8 
shows  the  appearance  of  these  segments  in  a  chick  embryo 
while  the  neural  groove  is  open.  The  segments  extend  from 
the  anterior  limit  of  the  head  as  far  back  as  the  neural  folds  are 
established ;  there  are  here  four  protovertebrae,  but  lying  in 
front  of  them  and  entirely  distinct  from  them  are  eleven  pairs 
of  the  primitive  neural  segments. 


Fig 


8.  —  Embryo  of  chick,  with 
open  neural  groove  and  three 
well-marked  mesoblastic  so- 
mites. The  neural  folds  are 
segmented  throughout  their 
extent. 


THE   PRIMARY  SEGMENTATION.  133 

These  segments  have  also  been  studied  in  living  embryos  of 
several  amphibia  in  stages  with  an  open  neural  groove.  They 
have  also  been  identified  in  the  early  stages  of  the  newt,  the 
frog,  and  the  torpedo. 

The  neural  segments  have  now  been  shown  to  occur  in  the 
very  early  stages  of  a  number  of  animals.  The  fact  of  their 
presence  in  these  early  stages  once  established,  they  assume 
new  importance.  They  have  a  too  definite  history  to  admit  of 
being  set  aside  as  mere  headings  or  undulations  of  no  meta- 
meric  significance.  The  fact  has  to  be  confronted  that  these 
neural  segments  are  the  early  stages  of  the  neuromeres,  whose 
characteristics  have  been  determined  by  a  number  of  observers. 
So  long  as  the  neuromeres  are  supposed  to  be  moulded  over 
the  mesoblastic  somites,  they  can  have  no  particular  importance 
in  the  problem  of  head  segmentation,  but  that  view  of  the 
neuromeres  is  an  assumption  made  without  a  knowledge  of 
their  early  history.  This  early  history,  now  made  known, 
places  them  in  a  new  light,  and,  taken  all  together,  the  neural 
segments  furnish,  I  think,  a  more  satisfactory  basis  for  inter- 
pretation of  metamerism  of  the  head  than  we  have  had  before. 

There  is  one  question  regarding  the  validity  of  these  seg- 
ments that  must  be  disposed  of  before  we  can  proceed  further. 
All  investigators  know  that  appearances  simulating  regular 
structures  may  be  produced  by  the  reagents  used  in  prepar- 
ing material  for  study  ;  and  the  question  comes  to  us.  Are  not 
these  segments  artifacts  produced  by  the  action  of  chemicals } 
Too  great  precaution  cannot  be  taken  in  sifting  this  matter  to 
the  bottom.  The  large  number  of  specimens  studied  as  a  basis 
for  the  facts  already  given  were  prepared  by  a  variety  of 
methods.  They  were  treated  with  reagents  well  known  to 
morphologists,  such  as  picro-sulphuric  acid,  picro-nitric,  Flem 
ming's  solution,  Davidoff's  corrosive-acetic,  chromic  acid  with 
a  trace  of  osmic,  corrosive  sublimate  removed  with  iodine  ;  and 
in  all  cases  the  segments  have  been  distinguishable,  not  in 
patches  but  in  such  condition  as  to  admit  of  being  counted, 
and  there  has  been  uniformly  the  same  number  of  segments 
in  the  head-region.  It  is  not  reasonable  to  assume  that  the 
different  reagents  would  all  produce  the  same  effect. 


134  BIOLOGICAL   LECTURES. 

The  history  of  these  segments,  in  Acanthias  and  the  chick, 
has  been  followed  very  carefully,  and  the  earliest  formed  ones 
have  been  traced  without  a  break  into  later  stages  and  identi- 
fied with  the  neuromeres.  If,  therefore,  the  segments  of  the 
open  neural  groove  stage  are  artifacts,  it  may  with  equal  force 
be  claimed  that  the  so-called  neuromeres,  which  are  their  later 
stages,  are  also  artificially  produced. 

It  should  also  be  borne  in  mind  that  similar  segments  exist 
in  correspondingly  early  stages  in  Amblystoma,  Rana  palustris, 
the  newt,  and  the  chick,  which  indicates  that  they  are  not  con- 
fined to  isolated  cases  but  are  a  fundamental  feature  of  verte- 
brate development. 

The  most  satisfactory  indication  of  their  true  nature  is  found 
by  observing  living  material  before  it  has  been  brought  into 
contact  with  any  reagent.  Fortunately,  the  chick  offers  at 
all  times  a  source  where  we  can  get  living  embryonic  material 
of  any  desired  age.  These  segments  have  been  repeatedly 
observed  in  living  chick  embryos  of  the  eighteenth  to  twenty- 
second  hour  of  incubation,  and  have  been  treated  with  re- 
agents while  they  were  actually  under  observation.  The  effect 
of  the  addition  of  picro-sulphuric  acid  is  to  render,  immediately, 
the  walls  of  the  neural  groove  opaque  and  more  clearly  defined, 
but  not  to  affect  the  number  or  arrangement  of  the  segments. 
The  same  segments  have  also  been  studied  in  living  embryos 
of  Amblystoma.  These  facts  are  conclusive  ;  if  the  segments 
exist  in  living  embryos,  they  are  veritable  anatomical  structures. 

Two  points  of  fundamental  importance  may  now  be  regarded 
as  established  :  (i)  that  the  neural  segments  are  present  in 
extremely  early  stages  of  vertebrates  where  they  have  not 
heretofore  been  recognized,  and  (2)  that  they  are  true  anatomi- 
cal structures  and  not  artifacts.  The  question  still  remains. 
Do  they  furnish  the  best  or  even  a  good  clue  to  the  number  of 
segments  in  the  primitive  brain  "^  If  so,  they  must  be  shown 
to  be  equally  important  in  this  direction  with  myotomes,  bran- 
chiae, and  cranial  nerves. 

In  estimating  the  claims  of  these  various  forms  of  segmental 
divisions  to  rank  as  the  primitive,  the  time  of  their  respective 
appearance    in    the  developmental  history  will  be  significant. 


THE   PRIMARY  SEGMENTATION.  I  35 

On  this  point  I  wish  to  observe  that  in  all  the  forms  studied, 
embracing  representatives  of  birds,  amphibia,  and  selachians, 
the  neural  segments  are  among  the  first  anatomical  structures 
to  be  established ;  before  the  vestiges  of  any  organs  have  ap- 
peared, the  embryo  is  divided  throughout  its  length  into  similar 
segments.  These  metameric  divisions,  therefore,  antedate 
myotomes,  branchiae,  cranial  nerves,  or  any  other  structures 
that  exhibit  metamerism.  They  persist  through  the  early 
stages  of  development,  and  become  definitely  related  to  seg- 
mental nerves  and  segmental  sense-organs.  In  the  light  of 
their  early  appearance  and  their  history,  I  think  we  are  justi- 
fied in  saying  they  are  the  most  satisfactory  traces  of  primitive 
metamerism  that  are  preserved  in  the  group  of  vertebrates. 

It  should  also  be  observed  that  the  entire  embryo  is  seg- 
mented, and  the  term  "metamerism  of  the  head"  should  be 
understood  to  signify  merely  regional  metamerism,  and  not  a 
different  kind  of  segmental  division  from  that  occurring  in  the 
rest  of  the  embryo. 

The  next  point  to  be  noted  with  regard  to  these  segments 
is  that  they  are  formed  independently  of  mesodermic  influence. 
I  have  shown  that  the  neural  segments  appear  much  earlier 
than  those  of  the  mesoderm,  and  that  they  extend  throughout 
the  embryo  ;  when,  however,  the  protovertebrae  appear  they 
are  localized,  and  are  formed  backwards  and  forwards  from  the 
point  of  their  first  appearance.  But  the  final  appeal  must  be 
made  to  sections.  A  careful  study  of  sections  of  shark  and 
chick  embryos  shows  that  the  mesoblast  is  not  divided  into 
protovertebrae  in  the  head,  even  after  that  region  is  completely 
segmented.  In  the  sharks  also,  the  neural  folds  that  are  so 
evidently  segmented,  are  at  first  wing-like  expansions  from 
the  body,  and  during  this  stage  no  mesoblast  enters  into  them. 
Therefore,  the  neural  segments  cannot  depend  upon  the  seg- 
mental folds  in  the  mesoblast.  The  combined  facts  place  the 
neural  segments  on  a  good  basis  for  independent  consideration 
as  survivals  of  primitive  segmentation. 

If  the  brain  walls  are  completely  exposed  by  removing  the 
overlying  tissues,  we  may  count  the  number  of  neural  seg- 
ments with  complete  satisfaction.     In  the  brain  of  shark  em- 


136  BIOLOGICAL  LECTURES. 

bryos  there  are  fourteen  pairs  of  segments  and  an  anterior 
unsegmented  tip  that  may  represent  a  single  pair  or  several 
consolidated  pairs.  This  is  a  larger  number  of  neural  seg- 
ments than  has  heretofore  been  counted  for  vertebrate  animals. 
It  approaches  more  nearly  the  number  of  head  myotomes  as 
determined  by  Dohrn  and  Killian. 

Finally,  we  are  to  conclude  from  a  study  of  the  neural  seg- 
ments that  the  vertebrate  brain  is  primitively  segmented  to 
its  anterior  tip  ;  that  its  segments  do  not,  at  first,  differ  from 
those  of  the  trunk,  —  in  other  words,  they  are  homodynamous 
with  those  of  the  spinal  cord,  —  and  that  there  are  in  sharks 
fourteen  pairs  of  segments. 

Whitman  has  shown  by  a  masterly  analysis  of  the  brain  and 
nervous  system  of  clepsine  that  the  entire  nervous  system  of 
annelids  may  be  regarded  as  a  series  of  brains,  and  that,  nor- 
mally, a  pair  of  these  nerve-centers,  or  brains,  belongs  to  each 
segment.  This,  taken  in  connection  with  the  facts  set  forth  in 
this  lecture,  enables  us  to  look  upon  the  human  brain,  not  as  a 
homogeneous  mass  of  tissue,  but  as  a  complex^  composed  of  an 
aggregation  of  about  fourteen  invertebrate  brains,  all  united 
into  a  working  whole.  We  are  to  understand  that  its  complex- 
ity has  been  brought  about  through  ages  of  responses  to  ex- 
ternal and  internal  influences,  and  its  perfection  of  physiological 
action  has  been  gradually  attained.  It  is  the  highest  product  of 
evolution,  the  goal  towards  which,  in  the  morphological  world, 
nature  has  been  working  for  countless  aeons  of  time. 


NINTH    LECTURE. 


THE   SEGMENTATION    OF   THE    HEAD.i 

PROF.   J.    S.    KINGSLEY. 

(Tufts  College.) 

One  of  the  perennial  questions  is,  "  How  many  segments  are 
there  in  the  vertebrate  head  ? "  We  have  long  realized  that 
the  body  of  a  vertebrate  is  made  up  of  segments  as  clearly 
marked  as  those  of  a  grasshopper  or  crayfish.  Is  the  head 
similarly  constituted  ? 

The  first  one  to  suggest  such  a  condition  was  that  mystical 
naturalist,  Oken.  As  he  tells  the  story,  he  was  walking  in  the 
Harz  Forest  in  1806,  when  he  found  the  blanched  skull  of  a 
sheep.  His  remark  upon  picking  it  up  was,  "  It  is  a  vertebral 
column."  The  next  year,  when  appointed  professor  extraordi- 
nary at  Jena,  he  took  for  his  inaugural  address  the  subject, 
"  The  significance  of  the  cranial  bones,"  in  which  he  main- 
tained that  the  skull  was  composed  of  three  vertebrae,  —  the 
eye,  jaw,  and  ear  or  tongue  vertebrae  of  his  nomenclature. 
Human  skulls  separated  into  these  three  vertebrae  may  be  had 
in  the  shops  to-day,  and  looking  at  one  of  them  we  are  struck 
with  the  genius  of  Oken's  idea. 

Thirteen  years  later  Gothe  claimed  the  discovery  as  his  own, 
but  time  has  settled  the  claim  in  Oken's  favor. 

Oken's  theory  maintained  at  least  a  tacit  acceptance  for 
many  years,  and  reached  its  highest  expression  in  the  work  of 
Owen.  Oken's  followers  tried  to  carry  it  further  and  to 
include  other  structures  than  the  skull.     Thus  in  the  trunk- 

1  The  complete  paper,  of  which  this  is  a  short  abstract,  will  be  published  else- 
where at  an  early  date,  with  full  references  to  the  literature,  etc. 


138  BIOLOGICAL   LECTURES. 

region  the  nerves  find  their  exit  between  the  vertebrae,  and  so 
they  should  do  in  the  cranial  region,  the  number  of  such  seg- 
mental nerves  being  of  course  one  less  than  the  number  of 
vertebrae  recognized  in  the  head.  So  those  who  followed  Oken 
arranged  all  the  cranial  nerves  in  two  groups,  while  those  who 
thought  they  saw  an  additional  or  nose  vertebra,  collected  the 
nerves  in  three  divisions.  Here  must  be  enumerated  the  labors 
of  Stieda,  Johannes  Miiller,  Stannius,  and  others. 

Stannius,  however,  took  another  set  of  structures,  the  gill 
clefts,  into  consideration,  and  although  he  admitted  only  three 
groups  of  these  nerves  (since  he  recognized  four  vertebrae)  he 
still  says  that  "the  number  of  the  branches  of  each  cranial 
nerve,  and  the  number  of  spinal-like  (segmental)  cranial  nerves 
is  determined  not  so  much  by  the  number  of  cranial  nerves  as 
by  that  of  the  visceral  arches." 

To  Gegenbaur  is  usually  given  the  credit  of  building  upon 
this  foundation,  but  we  must  not  forget  that  in  1869  Huxley 
claimed  that  no  part  of  the  skull  was  vertebral  in  its  nature, 
and  that  not  only  skeletal,  but  all  structures  should  be  invoked 
in  settHng  the  question.  It  would  not  do  to  make  the  bones 
the  basis,  and  work  everything  else  to  fit.  So,  dismissing  the 
bones,  Huxley  took  cranial  nerves  and  gill  clefts  as  his  basis. 
Behind  the  ear,  the  nerves  split  above  each  cleft,  and  send  a 
nerve  to  each  of  its  margins.  Here  the  relationships  are  clear, 
and  the  segments  can  readily  be  distinguished.  In  front  of 
the  ear,  however,  there  is  more  difficulty.  The  facial  nerve 
splits  in  the  same  way,  above  what  is  known  in  sharks  as  the 
spiracle,  a  cleft  which  persists  in  man  as  the  Eustachian  tube. 
For  the  next  nerve  in  front,  there  is  at  first  sight  no  cleft,  but 
Huxley  advanced  the  suggestion,  often  attributed  to  Dohrn, 
that  the  mouth  had  been  formed  by  the  coalescence  of  a  pair 
of  gill  slits,  and  upon  this  supposition,  this  nerve,  the  trigemi- 
nal, was  partly  brought  into  harmony.  But  not  all  of  it;  there 
are  branches  which  go  farther  forward,  and  for  a  cleft  for  these 
the  orbito-nasal  fissure  of  the  embryo  was  suggested.  Still 
another  cleft  still  farther  in  front  was  advocated,  so  that  Hux- 
ley recognized  in  the  head  nine  segments, —  four  in  front  of  the 
ear,  and  five  behind. 


THE   SEGMENTATION  OF   THE   HEAD.  139 

Two  years  later  (1871)  Gegenbaur  attacked  the  same  problem, 
and  between  his  results  and  those  of  Huxley  there  is  much 
similarity.  With  him  the  cranial  nerves  are  the  primary  test, 
and  he  tries  to  bring  the  gill  clefts  into  accordance  with  them. 

Of  the  cranial  nerves  modern  human  anatomists  recognize 
twelve  pairs,  known  by  name  and  number  as  follows:  — 

I.  Olfactory.  VII.  Facial. 

II.  Optic.  VIII.  Auditory. 

III.  Oculomotor  IX.  Glossopharyngeal. 

IV.  Trochlearis.  X.  Vagus  (Pneumogastric). 
V.  Trigeminal.  XI.  Spinal  Accessory. 

VI.    Abducens.  XII.    Hypoglossal. 

Like  Huxley,  Gegenbaur  at  once  threw  three  of  these  out  of 
discussion,  for  it  was  thought  that  the  nerves  of  special  sense — 
olfactory,  optic,  auditory — differed  from  the  rest  in  their  mode 
of  growth,  —  were,  in  fact,  outgrowths  of  the  brain  proper. 
Others,  from  the  nature  of  their  functions,  were  relegated  to  a 
secondary  position.  As  long  ago  as  1807,  Sir  Charles  Bell  had 
pointed  out  that  the  nerves  of  the  spinal  cord  had  two  roots, 
the  dorsal  one  with  an  enlargement,  or  ganglion,  the  ventral 
non-ganglionated,  and  that  these  roots  differed  entirely  in  their 
function.  Through  the  dorsal  root,  sensations  were  brought 
from  the  peripheral  parts  to  the  brain,  while  through  the  ven- 
tral root  the  actions  of  the  muscles  and  other  structures  were 
controlled.  Hence,  since  his  time,  these  roots  have  been  called 
respectively  sensory  and  motor.  In  the  brain-region,  however, 
this  distinction  of  roots  is  not  so  clearly  shown.  Some  of  the 
nerves,  like  the  third,  fourth,  and  sixth,  have  purely  motor 
functions,  and  these  motor  nerves  were  consequently  relegated 
to  a  secondary  position  ;  dorsal  or  sensory  roots  were  taken  as 
a  test. 

Now,  applying  these  ideas,  Gegenbaur  concluded  that  since 
the  vagus  nerve  was  distributed  to  several  gill  clefts,  it  must 
be  regarded  as  a  composite  nerve,  while  the  glossopharyngeal, 
supplying  a  single  cleft,  was  simple,  as  also  was  the  facial. 
The  trigeminal,  however,  had  too  many  branches  to  supply  a 
single    cleft,  and    so    this    was    regarded    as    a    double   nerve. 


140 


BIOLOGICAL   LECTURES. 


Another  feature  needs  mention.  The  gill  clefts  are  kept  from 
collapse  by  the  presence  of  skeletal  strengthening  bars  in  the 
tissue  between  them,  and  these  are  known  as  the  visceral  or 
branchial  arches.  But  there  were  not  enough  of  these  to  cor- 
respond with  all  the  nerves,  so  Gegenbaur  called  in  small  carti- 
lages found  in  the  lips  of  certain  sharks,  which  he  regarded  as 
remnants  of  such  arches.  His  whole  results  are  summarized 
by  him  in  a  table  :  — 


Primary 
Visceral 
Skeleton. 

Modified  Visceral  Skeleton. 

Nerve. 

1st  Arch 

1st 

upper  Labial  Cartilage 

Ramus,  2 

2d  Arch 

2d  upper 

and  I  St  lower  Labial 

Cartilages 

Ramus,  3 

-  J.  rigemini 

3d  Arch 

Mandibular  Arch 

Facial 

4th  Arch 

Hyoid  Arch 

Glossopharyngeal 

Sth  Arch 

I  St  Gill  Arch 

Ramus  branch,  i  ^ 

6th  Arch 

2d  Gill  Arch 

Ramus  branch,  2 

7th  Arch 

3d  Gill  Arch 

-Vagi 

Ramus  branch,  3 

Sth  Arch 

4th  Gill  Arch 

Ramus  branch,  4  ^ 

9th  Arch 

5th  Gill  Arch 

Gegenbaur  did  something  more  ;  he  gave  the  vertebrate 
theory  its  final  quietus,  for  he  pointed  out  that  in  the  lowest 
fishes,  where  one  would  naturally  expect,  were  Oken's  view 
true,  that  the  vertebrae  of  the  skull  would  be  most  typical,  the 
cranium  was  actually  a  solid  case  without  the  slightest  trace 
of  segmentation.  Further,  in  the  higher  groups,  cranial  "  ver- 
tebrae "  can  scarcely  be  spoken  of,  since  the  parts  of  which  they 
are  composed  are  largely  of  dermal  origin. 

Balfour  was  the  next  to  introduce  a  new  feature  into  the 
discussion.  As  is  well  known,  the  body  cavity  or  coelom. 
becomes  divided  dorsally  with  a  series  of  paired  pouches  which 
were  formerly  thought  to  give  rise  to  the  vertebrae,  and  hence 
were  called  protovertebrae.     They  are  now  known  to  produce 


THE   SEGMENTATION  OF   THE   HEAD. 


141 


the  muscles  of  the  trunk,  and  are  called  myotomes.  In  the 
trunk-region  these  are  the  most  markedly  segmental  of  any 
structures,  and  appear  very  early.  Balfour  pointed  out  that  the 
primitive  body  cavity  extended  into  the  head,  and  that  this  por- 
tion also  becomes  divided  in  much  the  same  way  as  that  of  the 
trunk.  So  with  him  "  head-cavities  "  are  the  test  of  cephalic 
segmentation.  As  there  is  much  similarity  between  his  results 
and  those  of  his  pupil  Marshall,  we  may  omit  a  discussion  of 
Balfour's  conclusions  and  give  those  of  Marshall  in  more  detail, 
merely  saying  that  Balfour  recognized  only  eight  segments  in 
the  head,  with  possibly  one  more. 

Marshall  uses  both  head-cavities  and  nerves  in  determining 
the  segments,  and  he  tried  to  bring  gill  slits  into  harmony  with 
these.  He  examined  those  nerves  admittedly  segmental,  and 
formulated  the  characteristics  which  a  segmental  nerve  must 
have.  The  results  to  which  this  brought  him  may  be  seen 
from  the  table,  but  some  explanations  may  be  pardoned. 


Segment. 

Nerve. 

Visceral 
Cleft. 

Visceral 
Arch. 

I   Preoral 

I  Olfactory 

Olfactory 

2  Preoral 

III  Oculomotor 

IV  Trochlearis 

Lachrymal 

Maxillary 

3  Oral 

V  Trigeminal 

Buccal 

4  Postoral 

VII   Facial 
VI  Abducens. 

Spiracular 

Mandibular 

Hyoid 

5  Postoral 

IX   Glossopharyngeal 

1st   Branchial 

1st     Branrhial 

6  Postoral 

X  Vagus,   I  St  branch 

2d    Branchial 

7  Postoral 

X  Vagus,  2d  branch 

3d    Branchial 

3d     Branchial 

8  Postoral 

X  Vagus,  3d  branch 

4th  Branchial 

4th   Branchial 

9  Postoral 

X  Vagus,  4th  branch 

5th  Branchial 

5  th    Branchial 

10  Postoral 

X  Vagus,  5th  branch 

6th  Branchial 

6th   Branchial 

II  Postoral 

X  Vagus,  6th  branch 

7th  Branchial 

142  BIOLOGICAL   LECTURES. 

First,  the  olfactory  nerve  was  brought  into  the  category  of 
the  segmental  nerves,  for  Marshall  points  out  that  in  its  devel- 
opment it  resembles  the  other  nerves,  and  is  not  a  prolongation 
of  the  brain  substance,  that  it  possesses  a  ganglion,  and  finally 
it  splits  distally  to  embrace  the  olfactory  organ,  just  as  the  facial 
or  glossopharyngeal  splits  to  pass  on  either  side  of  the  corre- 
sponding visceral  cleft.  From  this  relationship  he  is  led  to 
regard  the  olfactory  organ  as  a  gill  cleft,  comparing  the  folds  of 
the  Schneiderian  membrane  with  the  gills  themselves,  regard- 
less of  the  fact  that  the  one  is  ectodermal,  the  other  entodermal 
in  origin.  Second,  the  fact  that  the  trochlearis  arises  from  the 
dorsal  crest  of  the  brain,  and  that  the  oculomotor  was  thought 
to  be  primarily  connected  with  the  ciliary  ganglion,  leads  Mar- 
shall to  assign  these  motor  nerves  segmental  value.  The 
increase  in  segments  behind  is  due  to  the  fact  that  Marshall 
regarded  sharks  like  Heptanchus,  with  seven  gill  slits,  as  the 
more  primitive.  Regarding  the  rest  of  the  table  nothing  need 
now  be  said,  but  we  must  point  out,  thirdly,  that  the  history 
of  some  of  the  head-cavities  was  traced.  They  were  found  to  be 
connected  at  first,  and  their  separation  into  distinct  bodies  was 
shown  to  be  independent  of  the  formation  of  gill  slits.  The 
history  of  two  of  these  cavities  was  followed,  and  these  two 
were  found  to  give  rise  to  some  of  the  muscles  which  move 
the  eyeball. 

At  almost  the  same  time  that  Marshall  published  his  last 
paper.  Van  Wijhe  gave  to  the  world  the  results  of  his  studies, 
and  his  paper  is  one  of  the  most  frequently  quoted  in  connec- 
tion with  the  subject.  Head-cavities  form  the  basis  of  his 
work,  and  of  these  he  finds  nine  in  the  shark.  Since  his  num- 
bering of  these  has  been  almost  universally  followed,  we 
may  enumerate  them  with  some  detail,  giving  their  fates  as 
determined  by  Van  Wijhe.  The  first  pair  of  cavities  are  pre- 
mandibular  in  position,  and  in  the  later  development  give  rise 
to  the  muscles  rectus  superior,  inferior,  internus,  and  inferior 
oblique,  all  of  which  are  controlled  by  the  oculomotor  nerve. 
The  second  cavity  is  above  the  mandibular  arch,  and  sends  a 
branch  into  it.  This  cavity  gives  rise  to  the  superior  oblique 
eye  muscle,  and  is  innervated  by  the  trochlearis  nerve.     The 


THE   SEGMENTATION  OF   THE  HEAD. 


143 


third  cavity  lies  above  the  hyoid  arch,  and  is  finally  con- 
verted into  the  external  rectus  muscle,  controlled  by  the  abdu- 
cens  nerve.  The  fourth  cavity,  also,  lies  partly  in  the  hyoid 
arch.  The  rest  follow  in  regular  sequence,  interrupted  only  by 
the  auditory  organ.  Of  these  latter  the  fourth  and  fifth  degen- 
erate, the  sixth  produces  a  few  small  muscle  fibers,  while  the 
rest  unite  in  forming  the  ventral  prolongation  of  the  sterno- 
hyoid muscle.  From  these  facts  Van  Wijhe  concludes  that 
there  are  nine  segments  in  the  head,  and  that  the  hyoid  arch 
is  really  double. 

The  nerves  are  carefully  studied  in  connection  with  these 
somites.  The  olfactory  and  optic  nerves  are  omitted  from  the 
discussion,  since,  among  other  points,  they  are  in  front  of  the 
segments.  It  is  interesting  to  note  that  Van  Wijhe  shows 
that  the  optic  nerve  is  really  the  most  anterior  of  all  the  cranial 
nerves.  With  the  remaining  nerves  the  attempt  is  made  to 
distinguish  dorsal  and  ventral  roots.  The  results  can  be  seen 
in  this  condensed  copy  of  Van  Wijhe's  table  :  — 


i 

s-. 

Muscles  from  the 
Somite. 

Ventral  Nerve 
Root. 

Dorsal  Nerve 
Root. 

■ 

Rect.  sup.,  inf.,  int., 
and  inf.  oblique 

Oculomotor 

Ophthalmicus 
profundus 

2 

Superior  oblique 

Trochlearis 

Trigeminus 
less  Ophth.  prof. 

3 

Rectus  externus 

Abducens 

>     Acusticofacialis 

4 

none 

none 

5 

none 

none 

Glossopharyngeal 

6 

very  rudimentary 

not  recognizable 

' 

7 
8 

9 

1  Muscles   from   skull  to 
I     shoulder  girdle,  with 
1  anterior  part  of  sterno- 
J                  hyoid 

V      Hypoglossus 

Vagus 

Since  Van  Wijhe's  time  numerous  attempts  have  been  made 
to  add  to  his  structure,  and  in  most  of  these  the  nerves  have 
been  made  especial  objects  of  study,  and  the  results  would  be 


144  BIOLOGICAL   LECTURES, 

of  great  interest  had  we  opportunity  for  their  discussion.  Most 
of  these  deal  with  the  components  of  the  several  nerves,  with 
the  true  relationships  of  the  ciliary  ganglion,  with  the  position  to 
be  accorded  the  eleventh  nerve,  and  with  the  question  whether 
there  be  primitively  a  dorsal  root  to  the  hypoglossal.  The  head- 
cavities,  too,  are  discussed.  On  the  one  hand,  Rabl,  in  a  most 
valuable  summary  of  our  knowledge  of  the  whole  subject,  can- 
not find  all  of  Van  Wijhe's  cavities,  while  Dohrn  does  not 
regard  the  eye  muscles  as  comparable  to  the  muscles  of  the 
trunk,  —  a  conclusion  to  which  he  is  led,  among  other  reasons, 
by  his  view  that  the  lens  of  the  eye  is  a  modified  branchial 
cleft.  On  the  other  hand,  there  are  others  who  find  more  head- 
cavities  than  Van  Wijhe,  and  among  these  is  to  be  enumerated 
Miss  Piatt,  who  has  found  one  undoubted  cavity  in  front  of  the 
most  anterior  one  of  the  Dutch  anatomist.  Dohrn  and  Killian 
go  much  further,  and  find  eighteen  or  nineteen  of  these  struc- 
tures, but  their  work  can  be  dismissed  with  fevC"  words.  It  is,  in 
fact,  difficult  to  say  what  Dohrn' s  opinions  are.  He  is  most 
fertile  in  hypotheses,  and  he  never  takes  the  trouble  to  bring 
his  later  views  into  any  harmony  with  the  old  ones.  At  one 
time  every  thickening  of  ectoderm  or  entoderm  is  a  gill  cleft, 
again  every  hole  in  the  mesoderm  is  a  head-cavity,  in  the  third 
view  the  abducens  is  a  complex  of  at  least  six  nerves.  But  we 
are  getting  ahead  of  our  story. 

To  Froriep  and  Beard  we  owe  the  introduction  of  a  new  ele- 
ment into  the  discussion,  that  termed  by  Beard  **  branchial  sense- 
organs."  These  authors  independently  discovered  that  certain 
of  the  cranial  nerves  fuse  with  the  ectoderm  a  short  distance 
from  the  brain.  From  this  fusion  two  structures  are  developed  : 
one  the  ganglion  of  the  nerve,  from  which  the  fibers  of  the 
permanent  nerve  grow  back  into  the  brain  ;  the  other,  the  more 
superficial  portion,  forms  the  Anlage  of  a  sense-organ  situated 
in  the  branchial  region  just  above  a  gill  cleft.  These  sense- 
organs  are  regarded  by  Beard  as  segmental  in  nature,  and 
hence,  if  we  count  these  sense-organs,  we  at  the  same  time 
count  the  metameres  of  the  head.  So,  proceeding  on  this  basis. 
Beard  finds  eleven  segments  in  the  head,  and  arranges  the 
nerves  to  fit  in  the  way  which  can  readily  be  seen  from  the 


THE   SEGMENTATION  OF   THE   HEAD. 


H5 


diagram.  Among  the  interesting  features  is  the  recognition 
of  the  olfactory  as  a  segmental  nerve ;  though  the  nasal 
organ  is  not  regarded  as  a  branchial  cleft,  but  as  a  sense- 
organ  (cf.  Marshall).  The  facial  is  also  regarded  as  a  compound 
nerve,  and  the  auditory  nerve  is  segmental  because  it  supplies 
the  ear,  which,  like  the  nose,  is  in  the  same  category  of  seg- 
mental sense-organs. 


Z 

C/3 

Dorsal 
Nerve 
Root. 

Branchial 
Cleft. 

Nature  of 

Sense-Organ 

OF  Cleft. 

Ganglion. 

Head- 
Cavity. 

Ventral 
Nerve 
Root. 

I 

Olfactory 

none 

Olfactory 
Organ 

Olfactory 

none 

none 

II 

Radix  longa 
of  Ciliary 
Ganglion. 

none,  or 
Hypophysis 

Branchial 

Ciliary 

first 

Oculo- 
motor 

III 

Trigeminus 

Mouth 

Branchial 

Gasserian 

second 

Trochlear 

IV 
V 

)■  Facial  - 

absent 
Branchial 

Branchial 
Branchial 

r  Facial  ■ 

third 

Abducens 
none 

VI 

Auditory 

none 

Auditory 
Organ 

Auditory 

none 

none 

VII 

Glosso- 
pharyngeal 

1st  Branchial 

Branchial 

Glosso- 
pharyngeal 

? 

none 

VIII 

Vagus  I 

2d  Branchial 

Branchial 

Vagus  I 

none 

none 

IX 

X 

XI 

1  Vagus  II, 
\  III,  and 
IV 

3d,  4th,  and  J 
5th  Branchial 

Branchial 
Branchial 
Branchial 

1  Vagus  II, 
\  III,  and 

none 

none 

In  the  year  preceding  Beard's  paper  Ahlborn  maintained  that 
there  were  two  distinct  kinds  of  segmentation  in  the  head, — the 
one  of  the  mesoderm,  mesomery,  the  other  of  the  alimentary 
canal,  branchiomery, — and  that  these  two  were  independent  and 
not  causally  related.  His  views  have  had  not  a  little  influence 
on  subsequent  work,  but  it  must  be  said  that  it  is  not  a  difficult 
matter  to  answer  his  arguments,  and  indeed  to  show  that,  so 
far  as  our  present  knowledge  goes,  branchiomery  and  mesomery 
are  in  good  accord. 


146  BIOLOGICAL   LECTURES. 

Within  the  last  few  years  another  test  of  segmentation  has 
been  adduced,  that  of  the  segments  (neuromeres  or  encephalo- 
meres)  of  the  brain.  These  structures  had  been  noticed  by 
several  of  the  older  writers  upon  the  development  of  the  ner- 
vous system,  but  little  weight  was  given  them  until  Kupffer 
brought  them  prominently  into  notice  as  possibly  affording 
another  clue  to  the  segmentation  of  the  head.  The  idea  was 
further  carried  out  by  Beranek,  Orr,  Waters,  McClure,  Zimmer- 
mann,  and  others,  and  may  be  stated  in  its  present  form  some- 
what as  follows.  Besides  the  division  of  the  brain  into  its 
several  regions, — fore-brain,  'twixt-brain,  etc.,  —  this  structure 
shows  in  its  earlier  stages  another  segmentation,  most  plainly 
seen  in  its  lateral  walls.  For  instance,  the  medullary  region  is 
seen  to  consist  laterally  of  a  series  of  paired  enlargements,  sep- 
arated by  vertical  constrictions,  and  of  these  back  to  the  vagus 
there  are  six  (Orr)  or  seven  (Hoffmann).  These  neuromeres 
bear  a  definite  relation  to  the  nerves,  one  pair  of  these  arising 
from  each  neuromere,  except  that  between  the  acusticofacialis 
and  glossopharyngeal. 1  In  the  other  brain-regions  there  are 
four  more  of  these  enlargements,  two  in  the  primitive  fore-brain 
and  two  in  the  mid-brain,  —  a  total  of  eleven  back  to  and  includ- 
ing the  vagus. 

Hoffmann  has  made  a  most  important  discovery  in  connection 
with  the  development  of  the  cranial  nerves.  He  finds  that  the 
segmental  head  nerves  and  the  dorsal  roots  of  the  spinal  nerve 
arise  not  from  a  solid  neural  crest,  but  are  paired  segmental 
out-pocketings  {Ausstulpungen)  of  the  dorsal  part  of  the  ner- 
vous cord  itself.  For  the  details  of  the  matter  reference  must 
be  made  to  Hoffmann's  paper,  but  we  may  point  out  that  a  most 
important  inference  is  to  be  drawn  from  this  account.  Briefly, 
then,  the  segmental  cranial  nerves  (trigeminal,  glossopharyngeal, 
etc.)  arise  as  hollow  outgrowths  from  the  wall  of  the  cerebral 
tube ;  these  outgrowths  reach  the  skin  of  the  sides  of  the  head, 
fuse  with  it,  and  from  the  thickening  thus  produced  the  ganglion 
of  the  nerve  is  formed.  From  this  ganglion  the  permanent 
nerve  grows  back  to  the  brain,  the  primary  nerve  disappearing. 

1  Hoffmann  finds  an  Anlage  of  a  nerve  here  at  an  early  stage.  It  later  aborts, 
and  cannot  be  regarded  as  forming  a  part  of  the  auditory  nerve. 


THE   SEGMENTATION  OF   THE   HEAD.  147 

Exactly  the  same  conditions  occur  in  the  formation  of  the  optic 
nerve.  It  arises  as  a  hollow  outgrowth  from  the  dorsal  ^  part 
of  the  wall  of  the  brain,  which  reaches  the  ectoderm,  if  it  does 
not  actually  fuse  with  it.  From  the  distal  portion  of  this  out- 
growth is  formed  the  ganglionic  layer  of  the  retina,  correspond- 
ing exactly  to  the  Anlage  of  the  gasserian  ganglion,  and  from 
this  ganglionic  layer  the  observations  of  Keibel,  Froriep,  and 
Assheton  have  shown  that  the  permanent  optic  nerve  grows 
back  to  the  brain,  the  primitive  optic  stalk  becoming  aborted. 
So  that,  then,  there  appears  no  escape  from  the  view  that  the 
optic  nerve,  instead  of  being  a  structure  siii  generis,  is  clearly 
homologous  with  the  other  admittedly  segmental  cranial  nerves, 
—  trigeminal,  glossopharyngeal,  etc.  The  same  discovery  also 
opens  up  other  possibilities  ;  besides  offering  a  possible  explan- 
ation of  the  mooted  question  of  the  origin  of  the  vertebrate  eye, 
it  renders  it  necessary  to  take  into  account  in  considering  the 
neural  segmentation  of  the  head  the  little  understood  pinealis 
and  the  secondary  epiphysial  structures,  for,  as  Locy  has  shown, 
there  are  two  paired  outgrowths  from  the  brain  walls  behind, 
and  apparently  serially  homologous  with  the  optic  outgrowths, 
and  these  become  developed  into  what  we  may  collectively 
term  the  epiphysial  structures.  It  is  hence  possible  that  we 
are  to  look  in  this  region  for  some  of  the  long-sought  dorsal 
roots. 

Lastly  to  be  mentioned  is  the  earlier  segmentation  of  the 
neural  structures  discovered  by  Locy.  He  points  out  that  in 
the  very  early  stages  of  the  embryos  of  elasmobranchs,  batra- 
chians,  and  the  chick,  before  the  medullary  plate  has  begun  to 
close,  its  margins  are  ornamented  with  a  series  of  bead-like 
prominences,  and  that  the  series  of  these  are  continued  back 
into  the  trunk-region,  and  in  elasmobranchs  they  can  even  be 
traced  into  the  embryonic  rim  (affording  some  puzzling  prob- 
lems to  those  who  deny  concrescence  in  the  formation  of  the 
vertebrate  embryo).  In  the  expanded  head-plate  of  the  dog-fish 
he  finds  eleven  of  these  beads  on  either  side,  and,  following  the 
history  of  these  through  until  other  landmarks  come  into  view, 

1  Morphologically  dorsal  ;  the  later  hypertrophy  of  the  posterior  part  of  the 
dorsal  surface  forces  it  to  an  apparently  ventral  position. 


148  BIOLOGICAL   LECTURES. 

concludes  that  the  eleventh  of  these  coincides  with  the  position 
of  the  future  vagus.  The  fate  of  these  beads  is  followed  with 
some  detail,  and  is  regarded  as  of  paramount  importance  in 
settling  the  vexed  question  of  the  metamerism  of  the  head. 

It  may  be  that  further  observations  will  show  that  Locy  is 
right,  but  more  evidence  is  greatly  to  be  desired.  That  the 
structures  in  question  really  exist  is  beyond  doubt  ;  that  they 
have  the  significance  which  he  ascribes  to  them  is  far  more  prob- 
lematical. In  the  opinions  of  others  who  have  studied  them 
the  structures  are  less  regular  and  less  symmetrical  than 
described,  and  their  number  is  not  constant.  Besides,  there 
are  several  discrepancies  in  Locy's  figures,  which,  without 
explanation,  seem  to  invalidate  his  conclusions.  At  present  it 
seems  too  early  to  extend  the  term  neuromeres  to  include  these 
structures. 

It  is  now  nearly  ninety  years  since  the  question  of  the 
segmentation  of  the  head  was  first  broached.  Can  we  say  to- 
day how  many  segments  compose  this  complicated  structure } 
Several  times  it  has  seemed  that  the  answer  was  close  at  hand, 
but  as  frequently  has  the  investigation  of  other  features  thrown 
doubts  upon  the  previous  results  ;  and  to-day,  while  we  can  say 
that  there  are  certainly  more  than  the  three  or  four  of  Oken 
and  his  followers,  we  cannot  say  exactly  what  the  number  is. 
Before  the  answer  is  placed  beyond  a  doubt,  a  number  of  other 
questions  must  be  solved,  not  the  least  of  which  is  the  broader 
problem  of  the  origin  of  metamerism  and  the  relation  of  this 
condition  in  the  vertebrates  to  that  in  the  lower  forms. 


TENTH     LECTURE. 

BIBLIOGRAPHY,  — A    STUDY    OF    RESOURCES. 

CHARLES    SEDGWICK    MINOT. 

The  growth  of  science  depends  on  three  things  :  — 

First.    The  unknown,  which  is  discoverable. 

Second.    Raw  knowledge. 

Third.    Assimilated  knowledge. 

Our  laboratory  has  for  its  special  purpose  to  work  in  the 
first  of  these  fields,  and  every  one  of  you  ought  to  gain  largely 
from  the  discipline  and  inspiration  here  placed  at  your  com- 
mand. Bibliography  inventories  the  resources  of  the  second 
and  third  field,  while  text-books  are  intended  to  give  compre- 
hensive surveys  of  the  third.  Now  text-books  are  not  exces- 
sively numerous,  and  it  is  not  really  difficult  in  this  age  of 
incessant  advertisement  to  keep  tally  of  the  best  text-books, 
their  successive  editions,  and  new  rivals  in  one's  special  field 
of  biology.  Far  different  is  the  case  when  one  wishes  to 
retain  command  of  the  literature  of  original  research,  where 
the  gains  of  raw  knowledge,  as  I  have  called  it  above,  are 
made.  It  needs  but  little  experience  to  teach  even  the  begin- 
ning student  that  it  is  excessively  difficult  to  keep  track  of  the 
numerous  publications  in  which  the  current  work,  even  in  a 
narrow  field  of  biology,  is  recorded.  With  these  difficulties 
you  are  all  more  or  less  familiar,  and  know  from  your  own 
experience  that  they  are  due  chiefly  to  two  factors  :  first,  the 
very  great  number  of  the  publications;  second,  their  being 
scattered  without  law  or  order  in  many  different  publications 
issued  in  many  different  languages.  The  biological  bibliogra- 
pher is  like  an  explorer  in  a  forest, — he  finds  no  open  way 
to  travel,  but  must  laboriously  hunt  for  the  specimens  which 


150  BIOLOGICAL   LECTURES. 

belong  in  the  same  class  according  to  our  intellectual  systems, 
and  which  he  must  discover  as  they  lie  scattered,  unclassified, 
and,  all  too  often,  concealed.  In  passing,  let  me  add  that  one 
reason  for  the  increase  in  number  of  biological  articles  is  the 
change  in  the  publication  habits  of  the  present  as  compared 
with  those  of  a  generation  ago.  Formerly  the  preparation  of 
long  and  thorough  monographs  was  the  goal  of  ambitious 
investigators,  but  now  it  is  the  fashion  to  publish  instead  a 
succession  of  short  papers.  How  new  this  tendency  is  you 
will  appreciate  easily  by  remembering  that  we  have  now  a 
goodly  number  of  journals  devoted  exclusively  to  very  short 
papers,  such  as  the  Zoologischer  AnzeigeVi  Bota^iisches  Central- 
blatt,  Bibliographie  Anatomique^  and  many  more,  all  of  which 
date  back  only  a  very  few  years.  They  represent  a  class  of 
scientific  serials  which  twenty-five  years  ago  was  almost,  if 
not  quite,  unknown. 

It  will  be  the  main  purpose  of  this  lecture  to  point  out  the 
resources  we  have  for  finding  the  literature  of  a  given  bio- 
logical theme.  Before  beginning  this  task  let  us  consider 
briefly  what  a  biological  author  may  do  to  facilitate  making  a 
satisfactory  bibliographical  record  of  an  article  of  his  own. 
We  may  leave  apart  the  literary  and  scientific  qualities  of  the 
article,  not  because  we  fail  to  assign  them  their  due  prime 
importance,  but  only  because  we  are  looking  at  the  matter 
from  the  narrower  point  of  view  of  the  bibliographer.  Now, 
from  this  standpoint  there  are  five  points  which  seem  to  me  to 
deserve  special  attention. 

I.  The  title,  which  should  be  as  brief  as  possible  and  never- 
theless indicate  the  contents.  I  recently  noted  an  article 
entitled  A  Reply  after  Two  Years.  Under  what  head  will 
you  enter  it }  When  you  read  it  you  will  discover  that  it  deals 
with  the  embryology  of  turtles.  Such  a  title  is  unpardonable, 
for  it  will  cause  quite  unnecessary  trouble  to  hundreds,  per- 
haps thousands  of  people.  It  is  quite  as  bad  as  the  bugbear 
title  of  the  medical  bibliographer,  A^ Rare  Case.  There  are 
thousands  of  articles  on  that  subject,  but  what  is  it }  asks  the 
despairing  recorder.  For  brevity  of  title  it  is  surely  unneces- 
sary to   plead.     Every  one  who   has   had  to  cite  authorities 


BIBLIOGRAPHY,  — A    STUDY  OF  RESOURCES.       151 

knows  the  vexation  of  having  to  copy  a  long-winded  title. 
What  a  blessing  it  would  be  could  we  have  a  Linnaean  system 
for  the  nomenclature  of  biological  memoirs  as  well  as  of 
natural  species ! 

2.  The  table  of  contents.  The  use  of  tables  of  contents  for 
single  articles  of  forty  to  one  hundred  or  more  pages  is  a 
recent  and  excellent  innovation.  It  gives  a  detailed  summary 
of  the  arrangement  of  topics,  which  is  often  of  the  greatest 
convenience.  If  you  examine  the  ten  volumes  of  our  own 
JoiiVfial  of  Morphology^  you  will  find  many  articles  with  tables 
of  contents  prefixed.  Thus,  in  volume  ten  there  are  eleven 
articles,  five  of  which  —  those  by  Lillie,  Strong,  Fish,  Eycle- 
shymer,  and  Morgan  —  have  tables  of  contents,  and  of  the 
remaining  six,  only  one  exceeds  thirty  pages  in  length.  In 
European  articles  you  will  find  the  custom  less  frequently 
followed.  I  think  that  you  will  encounter  other  indications 
that  bibliographical  usages  are  more  advanced  in  America  than 
abroad.  May  we  not  attribute  this  difference  in  part  to  the 
examples  set  by  our  numerous  public  libraries } 

3.  Reprints  should  always  preserve  the  paging  of  the  original 
publication,  otherwise  they  cannot  be  used  for  consultation  or 
reference  without  needless  difficulty.  Publishers  are  wofully 
behindhand  in  this  matter,  and  usually  change  the  paging  in 
reprints,  sometimes  even  in  the  face  of  the  author's  protest,  as 
I  have  myself  recently  experienced.  If  the  paging  is  changed, 
how  can  we  refer  to  any  special  page  until  we  have  put  aside 
the  reprint  and  gone  to  the  original  publication,  the  page 
number  of  which  alone  has  the  right  to  be  cited } 

4.  References  to  other  authorities  need  careful  arrangement. 
If  they  are  few,  it  does  very  well  to  place  them  at  the  bottom 
of  the  page.  If  they  are  numerous,  the  best  place  for  them  is 
at  the  end  of  the  article,  in  alphabetical  order  by  authors. 
For  reference  numbers  for  the  single  articles,  there  are  two 
chief  systems  in  vogue.  One  system,  the  older  of  the  two, 
simply  numbers  the  articles  consecutively,  so  that  when  the 
article  is  completed  the  manuscript  must  be  revised  and  the 
proper  numbers  inserted  in  the  text.  Theoretically  the  system 
is  very  simple  and  convenient,  but  you  will  soon  learn  that  in 


152  BIOLOGICAL   LECTURES. 

practice  authors  are  apt  to  blunder  and  insert  wrong  numbers 
in  the  text.  One  set  of  references  has  to  be  used  while 
writing,  and  when  all  is  done  another  set  substituted,  and 
during  the  substitution  mistakes  are  not  infrequent.  The 
other  system  was  introduced  by  Professor  E.  L.  Mark,  and  has 
met  with  increasing  favor.  In  this  system  each  article  is 
identified  by  the  name  of  the  author,  the  date  of  publication, 
and  an  arbitrary  catalogue  sign,  which  last  may  be  a  single 
letter  or  digit.     For  example  :  — 

Mark,  E.  L.  81.1.  Maturation,  Fecundation,  and  Segmentation  of 
Limax  campestris,  Binney.  Bull.  Mus.  Comp.  Zool.,  VI,  171-625, 
Pis.  I-V. 

indicates  all  that  is  necessary.  The  figures  8 1 .  i  stand  for  the 
year  1881,  the  digits  indicating  the  century  being  omitted  for 
all  years  of  the  present  century  ;  and  the  single  digit  after  the 
period  indicates  the  arbitrary  order  of  entry,  —  in  this  case 
that  the  article  in  question  is  the  first  one  to  be  recorded  for 
that  author  and  year.  Should  a  second  article  published  by 
Professor  Mark  in  1881  appear  in  the  list,  it  would  be  81.2;  but 
were  it  in  1882,  it  would  be  82.1.  Professor  Mark  uses  a 
slightly  different  notation,  letters  serving  for  entry  signs  ;  thus 
the  paper  just  cited  would  be  recorded 

Mark,  E.  L.,  '8i% 

or, 

8i^     Mark,  E.  L. 

The  apostrophe  indicates  that  the  two  digits  are  omitted,  but 
now  that  this  system  has  been  widely  used,  the  apostrophe  may 
be  safely  left  off.  If  one  uses  Mark's  system,  the  references 
may  be  all  put  in  as  the  manuscript  is  written,  and  the  articles 
will  then  group  themselves.  Every  worker  should  have  a  card- 
catalogue  of  the  publications  in  his  own  field,  and  to  such  a 
catalogue  Mark's  system  is  peculiarly  adapted;  and  if  it  is  used, 
it  is  easy  to  enter  all  references  in  one's  manuscript,  giving 
each  paper  its  notation  from  the  catalogue.  While  preparing 
my  Human  Embryology  I  utilized  this  plan  for  the  several 
thousand  references  made  in  the  course  of  the  work,  and  can 


BIBLIOGRAPHY,  — A    STUDY  OF  RESOURCES.       I  53 

assure  you  that  in  practice  the  plan  is  very  convenient  and 
time-saving.  Some  of  the  best  investigators  prefer  other 
methods  of  citing  authorities.  I  can  only  recommend  the  two 
methods  just  indicated  as  best  in  my  own  judgment,  and  add 
that  it  is  more  important  to  have  a  good  method  than  to  have 
any  special  method. 

5.  Spare  your  readers  long  abstracts  of  previous  papers. 
Omit  most  of  the  abstracts  you  are  tempted  to  insert,  and 
make  those  you  do  give  as  brief  as  possible.  Abstracts  at  best 
are  inadequate  repetitions,  and  save  in  exceptional  instances 
should  be  avoided,  especially  since  there  has  developed  such 
an  elaborate  machinery  for  the  publication  of  abstracts  of  all 
important  and  many  unimportant  papers.  Too  often  an  abstract 
is  tacked  on  not  for  any  useful  purpose,  but  only  to  prove  that 
the  author  has  read  the  original.  On  the  other  hand,  a  compre- 
hensive review  of  the  results  collated  from  a  number  of  publi- 
cations may  often  be  valuable,  while  separate  abstracts  of  the 
same  papers  would  be  almost  valueless. 

About  the  arrangement  of  one's  own  library  let  me  inter- 
polate a  few  observations.  Of  course  if  a  library  is  small,  by 
which  I  mean  of  less  than  500  volumes  and  pamphlets,  no 
special  arrangement  is  needed,  beyond  what  may  be  the  out- 
come of  one's  personal  convenience.  And,  on  the  other  hand, 
if  your  library  be  very  large,  you  must  adopt  a  thorough  library 
system.  Most  working  naturalists  have,  however,  libraries  of 
moderate  size,  the  orderly  and  convenient  arrangement  of 
which  is  often  a  perplexing  problem.  The  perplexity  arises 
chiefly  from  the  accumulation  of  pamphlets,  which  are  a  very 
valuable  part  of  a  worker's  scientific  library,  being  for  the  most 
part  reprints  of  articles  in  his  own  special  field.  Now,  there 
are  three  prevalent  ways  of  treating  pamphlets. 

1.  Bind  them  in  volumes  by  authors. 

2.  Bind  them  in  volumes  by  subjects. 

3.  Arrange  them  in  boxes. 

Of  these  three  methods  the  last  is  the  simplest,  most  expedi- 
tious, and  for  a  library  without  a  catalogue  the  most  convenient. 
The  boxes  readily  serve  for  a  classification  either  by  authors  or 
subjects,   as   you   may  prefer.     Of  boxes  for  this  purpose  I 


154  BIOLOGICAL   LECTURES. 

recommend  either  the  cheap  pamphlet  cases  of  Manilla  paper, 
sold  by  stationers  everywhere,  or  else  the  more  convenient 
wooden  box  devised  by  Dr.  Bowditch,  and  which  has  the 
advantage  that  when  it  is  opened  the  titles  of  the  pamphlets 
face  you. 

[Since  this  lecture  was  delivered  I  have  used  another  form 
of  pamphlet  box,  which  seems  preferable  to  those  mentioned. 
It  is  a  box  made  of  whitewood,  covered  with  marbled  paper  ; 
it  measures  4x11x7^  inches;  it  has  a  common  drawer- 
handle  on  the  back,  and  is  open  at  the  front, ^  Such  boxes  are 
placed  on  shelves,  like  volumes  ;  they  present  a  neat  appearance, 
and  are  easily  pulled  out  or  replaced.  It  would  be  desirable  to 
have  a  card-holder  on  the  back  to  indicate  the  contents  upon 
cards,  which  can  be  changed  as  convenient.] 

Every  professional  biologist  ought  to  have  a  card-catalogue, 
serving  the  double  purpose  of  a  bibliography  and  a  catalogue 
of  his  library.  I  can  probably  lay  my  suggestions  before  you 
most  rapidly  by  describing  my  own  system,  which,  with  your 
permission,  I  will  now  do.  This  system  has  worked  satisfac- 
torily, but  I  can  by  no  means  claim  for  it  that  it  is,  like 
Pangloss'  world,  the  best  of  all  possible  systems.  The  library 
is  arranged  in  several  groups,  and  the  pamphlets  in  each  group 
are  arranged  alphabetically  by  authors,  and  under  each  author 
by  Mark's  chronological  system.  First  the  pamphlets  are  sep- 
arated into  two  primary  divisions,  those  which  are  not  cata- 
logued and  those  which  are  catalogued.  Those  pamphlets 
which  do  not  immediately  concern  my  own  lines  of  study  are 
not  catalogued,  but  are  simply  classified  in  Bowditch  boxes  by 
subjects.  Thus  I  have  a  box  for  biographical  notices,  for  path- 
ology, botany,  systematic  entomology,  microscopical  methods, 
etc.,  and  hundreds  of  pamphlets  are  kept  readily  accessible. 
The  remaining  pamphlets  are  all  catalogued  on  cards  of  the 
larger  standard  library  size,  made  of  cardboard,  not  paper. 
Were  I  to  start  over  again,  I  should  unhesitatingly  use  the 
smaller  card,  12.5x5.0  cm.  (about  5x2  inches),  of  stiff  paper. 

1  Pamphlet  boxes  as  described,  but  without  handles,  may  be  obtained  of  the 
Library  Bureau  in  Boston.  In  fastening  on  the  handle,  fairly  large  screws  should 
be  used,  which  may  be  cut  off  so  as  not  to  project  inside  and  tear  the  pamphlets. 


BIBLIOGRAPHY,— A    STUDY  OF  RESOURCES.       155 

The  plan  on  which  the  cards  are  written  is  indicated  by 
the  following  form  :  — 

Whitman,  Charles  O.  M.  1893. i 

The  Inadequacy  of  the  Cell-Theory  of  Development. 
!  Journ.  Morph.,  VIII,  639-658. 

The  upper  right-hand  corner  contains  the  catalogue  number 
(Mark's  system),  the  M  showing  that  the  pamphlet  is  in  my 
collection,  and  that  the  card  is  not  merely  a  bibliographical 
one.  It  is  better  to  have  the  catalogue  number  on  the  left,  for 
it  is  then  less  likely  to  be  covered  by  the  hand  in  turning  over 
the  cards.  The  Roman  numerals  are  used  to  designate  the 
volume,  the  Arabic  the  pages.  When  there  are  plates,  the 
numbers  of  those  are  given  also.  The  exclamation  point  at 
the  left  indicates  that  the  card  has  been  verified  by  comparison 
with  the  original  publication.  All  my  catalogued  pamphlets 
are  divided  into  three  sets:  (i)  octavo  unbound  pamphlets; 
(2)  octavo  bound  pamphlets ;  (3)  quarto  pamphlets,  whether 
bound  or  unbound.  When  a  pamphlet  is  bound,  the  card  is 
marked  *'  Bd."  In  each  of  the  three  sets  the  pamphlets  are 
arranged  by  authors,  and  those  of  each  author  chronologically. 
Thicker  pamphlets  are  bound  singly,  thinner  pamphlets  several 
together,  —  but  binding  many  papers  in  one  volume  is  sys- 
tematically avoided.  The  binding  costs  from  twelve  to  eigh- 
teen cents  ;  the  backs  are  plain  black  cloth,  with  a  white  paper 
label,  on  which  the  author's  name  and  the  catalogue  numbers 
of  the  pamphlets  are  written  by  hand  ;  the  sides  are  covered 
with  marbled  paper.  The  unbound  octavo  pamphlets  are  kept 
in  Manilla  paper  pamphlet-boxes.  From  time  to  time  I  look 
them  through  to  select  those  which  I  wish  to  have  bound. 

The  system  described  is  simple,  and  to  me  it  has  seemed 
convenient  and  altogether  satisfactory,  so  that  I  am  ready  to 
recommend  it,  though  of  course  some  other  system  may  be 
equally  good  for  private  use. 

My  catalogue  serves  me  also  as  a  bibliography,  and  I  main- 
tain a  list  of  titles,  which  are  copied  from  my  cards  and 
grouped  under  subjects.     In  this  way  I  compiled  my  Bibliog^- 


156  BIOLOGICAL   LECTURES. 

raphy  of  Vertebrate  Embryology^  which  was  published  by  the 
Boston  Society  of  Natural  History  in  1893.  It  contains  3555 
titles,  and  it  may  interest  you  to  know  that  I  have  collected 
since  its  publication  upwards  of  a  thousand  titles  to  be  added 
to  it.  As  this  work  is  intended  to  result  in  publication,  the 
results  are  written  out  on  sheets  of  paper,  each  sheet  for  one 
subject  only  ;  were  it  not  for  publication,  I  should  use  cards 
for  the  subject  catalogue  also. 

Let  us  pass  to  our  main  topic,  a  discussion  of  the  means  of 
looking  up  the  literature  of  a  given  subject  in  the  domain  of 
animal  morphology  or  physiology ;  in  regard  to  other  divisions 
of  the  wide  territory  of  biology  I  am  not  competent  to  advise 
you.  We  will  pass  in  review :  (I)  the  standard  bibliogra- 
phies ;  (II)  incidental  bibliographies,  given  in  connection  with 
special  memoirs,  etc.  ;  (III)  current  bibliographies,  which  we 
can  divide  into  two  groups  :  {A)  those  appearing  annually,  and 
{B)  those  appearing  periodically  at  intervals  of  less  than  a  year. 

I.  Standard  Bibliographies.  —  The  purpose  and  character 
of  these  is  so  evident  that  it  is  only  necessary  to  enumerate 
them.     They  are  :  — 

1.  W.  Engelmann.  Bibliotheca  historico-naturalis .  i  vol. 
8vo.      Leipzig,  1846.     Covers  the  literature  of  1 700-1 846. 

2.  Carus  und  Engelmann.  Bibliotheca  zoologica.  2  vols. 
8vo.      1 86 1.     Covers  the  years  of  1 846-1 860. 

3.  Taschenberg.  Bibliotheca  zoologica  II.  Twelve  parts, 
with  pages  1-3888,  have  been  issued,  the  mammals  not  being 
yet  reached.     It  is  the  continuation  of  Carus  and  Engelmann. 

4.  Hagen.  Bibliotheca  ent  onto  logic  a.  Die  Literatur  liber 
das  ganze  Gebiet  der  Entomologie  bis  zum  Jahre  1862.  2  vols. 
8vo.      1862. 

5.  MiNOT.  Bibliography  of  Vertebrate  Embryology.  4to. 
Boston  Society  of  Natural  History.      1893. 

Important  help  in  finding  a  paper,  when  the  author  is  known, 
is  given  by  the  Catalogue  of  Scientific  Papers,  issued  by  the 
Royal  Society  of  London,  in  spite  of  the  enormous  number  of 
its  omissions.     This  catalogue  comprises,  in  all,  three  series  of 


BIBLIOGRAPHY,  —  A    STUDY  OF  RESOURCES.       I  57 

large  quarto  volumes.  The  first  series,  in  six  volumes,  deals 
with  the  literature  of  1 800-1 863;  the  second  series,  in  two 
volumes,  with  the  literature  of  1 864-1 873  ;  the  third,  and  still 
unfinished  series,  with  the  literature  of  1 874-1 883.  It  arranges 
the  papers  by  authors,  numbering  those  of  each  author  con- 
secutively through  the  three  series.  There  is  no  classification 
by  subjects,  and  no  subject  index,  so  that  one  can  obtain  a 
reference  only  in  case  the  author  is  correctly  known.  On  the 
score  of  convenience  it  is  to  be  regretted  that  the  Royal 
Society  did  not  imitate  the  compact  American  model  of  library 
catalogue,  but  on  the  contrary  adopted  a  type  and  arrange- 
ment which  has  rendered  their  volumes  needlessly  bulky  and 
inconvenient. 

Three  other  works,  though  not  strictly  bibliographical  in  the 
sense  of  those  above  mentioned,  deserve  to  be  named  here. 
These  are :  — 

1.  Nomenclator  zoologicus  continens  nomina  systematica 
generum  animalium  tam  viventium  quam  fossilium,  auctore 
L.   Agassiz.     Soloduri,    1 842-1 846.     2d  edition,    1848. 

2.  Nomenclator  zoologicus,  etc.  A  comite  Augusto  de 
Marschall. 

3.  Nomenclator  zoologicus,  by  Samuel  H.   Scudder. 

Agassiz's  work  contained  (2d  edition)  32,964  entries,  Mar- 
schall's  19,966,  Scudder's  about  80,000.  Mr.  Scudder's  work, 
like  everything  done  by  the  distinguished  president  of  the 
Marine  Biological  Laboratory,  is  a  monument  of  painstaking 
industry  and  well-directed  thoroughness,  and  it  should  be  at 
hand  for  every  zoologist  to  consult  who  has  a  new  genus  to 
name,  so  that  needless  duplication  may  be  avoided.  Scudder's 
Nomenclator  was  published  as  Bulletin  No.  19  of  the  United 
States  National  Museum.  It  was  based  on  Agassiz's  Nomen- 
clator, together  with  the  manuscript  addenda,  which  Professor 
Agassiz  had  accumulated  during  a  long  course  of  years.  It 
covers  the  names  introduced  down  to  the  close  of  the  year 
1879.     For  later  names  consult  the  Zoological  Record. 

Finally,  we  are  indebted  to  Mr.  Scudder  for  still  another 
work,  which  you  will  often  find  invaluable,  namely,  his  Cata- 


158  BIOLOGICAL   LECTURES. 

logue  of  Scie7itific  Serials  of  all  Countries,  inchiding  the  Trans- 
actions of  Learned  Societies  iji  the  Natural,  Physical,  and 
Mathematical  Sciences,  l6jj-l8y6,  published  by  the  Library  of 
Harvard  University  in  1879. 

II.  Incidental  Bibliographies,  or  lists  of  authorities  given  in 
special  works.  As  you  know,  every  important  article  gives 
more  or  less  extensive  references  to  the  previous  literature, 
and  one  does  not  need  long  experience  to  appreciate  the 
immense  advantage  of  this  custom.  Especially  to  the  great 
monographs  do  we  turn  for  such  references,  and  I  may  direct 
your  attention  especially  to  the  splendid  series  known  as  the 
Fauna  and  Flora  of  the  Gulf  of  Naples,  which  is  in  our  library. 
The  more  important  text-books  usually  give  carefully  selected 
lists  of  the  more  important  papers.  You  will  find  such  in 
McMurrich's  Invertebrate  Morphology,  Wiedersheim's  or  Gegen- 
baur's  Comparative  Anatomy,  Hertwig's  Embryology,  Korschelt 
and  Heider's  Embryology  of  Invertebrates,  and  other  similar 
hand-books.  But  among  all  works  of  this  class  there  stand 
two  which  are  preeminently  valuable  for  their  helpfulness  in 
guiding  us  to  morphological  and  zoological  literature ;  one  is 
Milne-Edwards'  Physiologic,  in  fourteen  volumes  (G.  Masson, 
Paris,  1 857-1 881).  This  great  work  is  a  rich  treasury  of 
references,  especially  to  the  older  literature,  which  it  is  some- 
what the  fashion  to  overlook,  although  it  often  contains  things 
which  have  been  forgotten,  and  which  you  would  do  well  to 
make  the  acquaintance  of,  if  only  to  learn  that  the  broad 
foundations  of  our  science  were  all  laid  before  any  of  us  were 
born.  Milne-Edwards  was  thoroughly  versed  in  the  zoological 
literature  of  his  time,  with,  however,  a  curiously  abrupt  limit 
at  about  1858.  In  fact,  though  his  work  contains  a  very  large 
number  of  references  to  papers  later  than  1858,  the  proportion 
of  omissions  is  strikingly  larger  than  for  papers  issued  before 
that  date.  You  will  find  the  consultation  of  these  early 
authorities  especially  valuable  for  anatomical  information  con- 
cerning all  classes  of  animals.  The  present  generation  is  so 
devoted  to  comparative  morphology  and  general  principles  that 
real  anatomical  knowledge  of  animals  has  become  almost  a 
rarity.     Thus   I  find  young  men  who  can  discuss  glibly  the 


BIBLIOGRAPHY,  — A    STUDY  OF  RESOURCES.       159 

problem  of  the  morphological  (segmental)  value  of  the  tri- 
geminal nerve,  and  yet  cannot  give  exact  information  concerning 
it^  anatomical  disposition  in  any  animal. 

Henri  Milne-Edwards  was  born  in  1800,  and  died  in  1885. 
He  was  a  typical  naturalist,  trained  under  the  influence  of  the 
great  Cuvier,  and  as  a  naturalist  looked  upon  animals  very 
differently  from  the  modern  morphologist,  with  whose  ways  he 
was  as  little  able  to  sympathize  as  with  the  views  of  Darwin. 
In  many  respects  the  naturalist  had  a  broader  conception  of 
zoology  than  now  prevails,  for  to  him  the  earth  was  a  whole,  in 
which  rocks,  animals,  and  plants  all  had  their  parts  and  mutual 
relations,  and  the  comprehension  of  these  relations  was  the 
ideal  for  the  attainment  of  which  he  strove.  You  will  find 
in  Milne-Edwards'  writings  typical  illustrations  of  the  scientific 
attitude  of  zoologists  before  the  Darwinian  theory  was  put 
forth,  and  from  these  illustrations  one  preserves  an  impression 
of  loss  which  has  befallen  us  through  our  surrendering  too 
fully  to  the  biological  tendencies  and  fashions  of  our  day.  It 
is  therefore  doubly  profitable  to  consult  Milne-Edwards'  Physi- 
ologies for  it  not  only  collates  much  information  not  else- 
where well  united,  but  also  presents  it  from  a  point  of  view 
novel  to  most  of  us,  although  it  was  the  point  of  view  of 
those  great  men  who  created  not  only  zoology  in  the  nar- 
rower sense,  but  also  physiology,  comparative  anatomy,  and 
palaeontology. 

The  other,  Bronn's  Thierreichy  is  doubtless  well  known  to 
you  all.  It  is  a  work  on  a  vast  plan,  aiming,  as  it  does,  to 
present  a  comprehensive  summary  of  our  knowledge  of  the 
morphology,  including  also  the  classification,  distribution,  and 
biology  of  all  classes  of  the  animal  kingdom.  The  volumes  are 
issued  in  thin  parts,  each  volume  dealing  with  a  single  class. 
It  thus  happens  that  many  years  have  elapsed  between  the 
beginning  and  the  completion  of  a  volume,  —  the  extreme  being 
the  volume  on  Crustacea,  which  was  begun  in  1866  and,  al- 
though it  has  acquired  great  bulk,  is  still  unfinished,  though  its 
author.  Professor  Gerstaecker,  of  Greisswald,  had  at  the  time 
of  his  death  nearly  terminated  the  work.  The  status  of  Bronn's 
Thierreich  at  the  present  time  is  as  follows  :  — 


l6o  BIOLOGICAL   LECTURES. 

Protozoa,  first  edition,  by  Bronn,  completed  1S59. 
Protozoa,  second  edition,  by  Biitschli,  completed  1889. 
Sponges,  by  Vosmaer,  completed  1887. 

Actinozoa  (coelenterates  and  echinoderms),  by  Bronn,  completed 
i860. 

Coelenterates,  second  edition,  by  Chun  (pts.  i-io). 
Echinoderms,  second  edition,  by  Ludwig  (pts.  1-19). 
Malacozoa,  by  Bronn  and  Keferstein,  completed  1866. 
Mollusca,  second  edition,  by  Simroth  (pts.  1-20). 
Tunicates,  second  edition,  by  Seeliger  (pts.  1-3). 
Worms,  by  Pagenstecher  and  Braun  (pts.  1-37). 
Crustacea,  by  Gerstaecker,  first  half,  completed  1879. 
Crustacea,  by  Gerstaecker,  second  half  (pts.  1-46). 
Fishes,  by  Hubrecht  (pts.  1-4). 
Amphibia,  by  Hoffmann,  completed  1878. 
Reptiles,  by  Hoffmann,  completed  1890. 
Birds,  by  Gadow  (pts.  1-49). 
Mammals,  by  Giebel  and  Leche  (pts.  1-41). 

In  all  these  volumes  the  literature  is  abundantly  cited,  and 
they  usually  include  exceedingly  valuable  bibliographies,  in 
most  cases  classified  by  subjects.  When  we  consider  the  value 
of  these  lists  of  authorities,  and  in  our  minds  add  the  value  of 
Bronn' s  Thierreich  as  the  fullest  existing  repository  of  zoologi- 
cal facts,  we  necessarily  rank  this  invaluable  compendium  among 
the  few  books  indispensable  to  every  zoological  laboratory. 

III.  Current  Bibliographies y  or  periodicals  devoted  wholly  or 
in  great  part  to  recording  the  current  literature  in  a  given 
field.  We  may  consider  such  bibliographies  conveniently 
under  two  heads  :  firsts  annual  publications ;  second^  periodical, 
that  is,  issued  at  shorter  intervals. 

A.  Annual  Publications. — The  succession  of  these  may 
be  said  to  have  been  fathered  by  Miiller's  Archiv  fur  Anatomie, 
Physiologie  und  wissenschaftliche  Medizin.  Miiller's  Journal 
was  the  continuation  of  Reil's,  Reil  and  Autenrieth's,  and 
J.  F.  Meckel's  ArcJiiv.  It  was  begun  in  1834,  and  is  continued 
to-day,  but  in  1877  was  divided  into  two  Abtheilungen  {Anato- 
mische  and  Physiologische),  each  making  an  annual  volume. 
The  whole  series  constitutes  the  most  important  morphological 
and  physiological  single  publication  in  the  world.     Johannes 


BIBLIOGRAPHY,  — A    STUDY  OF  RESOURCES.       l6l 

Miiller  remained  the  editor  from  1833  to  1858.  He  was  one 
of  the  greatest  scientific  men  Germany  has  produced,  and  ranks 
as  pioneer  and  founder  of  three  sciences  :  of  comparative  anat- 
omy and  embryology, — or,  as  we  now  prefer  to  say,  morphol- 
ogy,— of  experimental  physiology,  and  of  scientific  pathology. 
He  was  endowed  with  that  genius  for  observation  and  induction 
which  alone  enables  a  man  to  become  a  great  leader  in  natural 
science.  In  the  first  volume  of  his  Archiv  he  gives  a  "  Jahres- 
bericht  ueber  die  Fortschritte  der  Anatomischen-physiolo- 
gischen  Wissenschaften  im  Jahre  1833."  Since  that  time, 
Germany  has  supplied  us  our  most  important  annual  records 
or  summaries.  The  Jahresberichte  of  Johannes  Miiller  are 
most  interesting  reading,  even  to-day ;  they  are  remarkable  for 
the  clearness  with  which  the  important  points  are  brought  to 
notice.  In  later  years  he  engaged  various  collaborators  in  this 
work,  among  whom  we  find  Siebold,  Keferstein,  Reichert,  and 
others.     With  Miiller's  death,  in  1858,  these  reports  closed. 

Their  place  was  taken  by  two  series  of  Reports,  one  issued 
in  connection  with  the  ArcJiiv  fur  NatiLrgeschichte^  the  other  in 
connection  with  the  Zeitschrift  fur  Rationelle  Medizift.  The 
former  journal  was  founded  in  1835  ^Y  Professor  Wiegmann, 
of  Berlin,  and  originally  published  with  each  Heft  a  report  of 
progress  in  some  field  of  zoology  or  botany ;  with  its  second 
year  it  began  the  system  followed  up  to  the  present  time,  of 
issuing  two  volumes  a  year,  the  second  made  up  entirely  of 
reports  for  various  branches  of  biology.  Of  late  years  the 
Archiv  fur  Naturgeschichte  has  shown  a  predominant  entomo- 
logical tendency,  both  in  its  original  articles  and  reports, 
although  it  still  continues  to  cover  a  wide  range,  except  that 
botany  has  entirely  dropped  out.  Its  reports  are  often  very 
late  in  appearing,  and  are  irregularly  issued ;  thus  the  part 
published  in  November,  1894,  gives  the  reports  on  entomology 
for  1893,  on  carcinology  for  1891,  1892,  and  1893.  In  spite  of 
all  these  peculiarities  you  will  find  these  Berichte  often  valuable. 

The  Zeitschrift  fur  Rationelle  Medizin  was  a  first-class  scien- 
tific serial.  It  entered  upon  its  third  series  in  1857,  and  then 
began  issuing,  as  an  annual  volume,  a  ^^ besondere  Abtheilung'' 
the  first  of  which  bears  this  title  :  ^^  BericJit  ilber  die  Fortschritte 


1 62  BIOLOGICAL   LECTURES. 

der  Anatomie  und  Physiologie  im  Jahre  l8^6.  Herausgegeben 
von  Dr.  J.  Henle^  Professor  in  Gottingejt,  tmd  Dr.  G.  Meiss?ier, 
Professor  in  Basel!'  We  have  here  a  consolidation  of  interests, 
for  these  Berichte,  by  Henle  and  Meissner,  had  already  appeared 
several  years  independently.  They  continued  in  connection 
with  the  Zeitschrift  until  1872  (literature  of  187 1).  I  have 
been  informed  that  the  cessation  of  the  publication  was  due 
to  lack  of  sufficient  financial  support.  They  were,  however, 
immediately  replaced  by  a  new  series  of  Jahresberichte,  edited 
by  Hoffmann  and  Schwalbe,  later  by  Hermann,  of  Konigsberg, 
and  Schwalbe.  This  new  series  continued  for  twenty  years, 
and  it,  like  its  predecessor,  ceased,  but  unfortunately  has  no 
successor,  except  for  the  physiological  part.  But  th^sQ  Jahres- 
berichte  are,  to  a  certain  extent,  replaced  on  the  morphological 
side  by  the  Ergebnisse  der  Anatomie  und  Entwickelungsge- 
schichte,  edited^by  Fr.  Merkel  and  R.  Bonnet,  which  constitute 
the  Zweite  Abtheilung  of  the  Anatomische  Hefte.  Of  the 
^^ Ergebnisse''  three  volumes  (1891-93)  have  appeared.  These 
volumes  give  comprehensive  summaries  of  groups  of  articles. 
The  physiological  part  of  the  fahresbefichte  has  been  con- 
tinued in  a  very  condensed  form  by  Professor  Hermann  in  his 
newly  inaugurated  series. 

With  the  progress  of  years  the  annual  reports  have  gradu- 
ally changed  in  character.  The  early  ones  were  narrative  in 
form  and  critical  in  character.  Thus,  in  the  first  report  by 
Johannes  Miiller,  he  relates  the  discussions  between  the  sober- 
minded,  and  perhaps  dogmatic  Cuvier,  and  the  brilliant  but 
erratic  Geoff roy  Ste-Hilaire,  to  whom  we  habitually  refer 
erroneously  as  Ste-Hilaire ;  and  Miiller  indicates  his  estimate 
of  both  these  eminent  naturalists,  and  finds  occasion  from  time  to 
time  to  interpolate  opinions,  and  even  observations  of  his  own. 
But  gradually  the  personality  of  the  reporter  is  withdrawn, 
until  it  has  become  the  admitted  requirement  that  all  analyses 
should  be  impersonal  abstracts.  In  the  Jahresberichte  of  the 
present  this  requirement  is  entirely  fulfilled,  with  only  very 
rare  exceptions. 

There  are  also  two  series  of  ^-^^oSA  Jahresberichte^  which  the 
active  worker  in  biology  and  zoology  will  find  indispensable  in 


BIBLIOGRAPHY,  — A    STUDY  OF  RESOURCES.       1 63 

connection  with  certain  lines  of  work.  The  first  of  these  is 
edited  by  Professor  Baumgarten,  formerly  of  Konigsberg,  at 
present  of  Tubingen.  This  annual  bears  the  somewhat  lengthy 
title,  Jahresbericht  iiber  die  Fortschritte  in  der  Lehre  von  den 
patJiogenen  Miki^oorganismen,  timfassend  Bacterien^  Pilze  tind 
Protozoen.  The  first  volume  covered  the  literature  for  1885, 
and  the  ninth  volume  (for  1893)  is  now  in  course  of  publica- 
tion. The  second  of  these  is  the  Jahresbericht  iiber  die  Fort- 
schritte der  Thierchemie,  edited  by  Prof.  Richard  Maly,  of 
which  the  first  volume,  published  in  1873,  at  Vienna,  covers 
the  literature  for  1871.  The  series  is  still  continued,  but  the 
volumes  make  their  appearance  considerably  belated. 

Finally,  I  ought  to  allude  —  I  cannot  do  more  than  that  — 
to  the  botanical  Jahresbericht y  the  first  of  whose  bulky  volumes 
was  issued  in  1873  by  Professor  Just.  In  appearance  and 
arrangement  of  the  contents  this  series  has  been  closely 
imitated  by  the  younger  zoological  Jahresbericht  (begun  in 
1879). 

We  now  come  to  the  two  great  zoological  records.  Those 
which  have  been  mentioned  above  are  (with  the  exception  of 
the  Botanischer  Jahresbericht  and  the  reports  in  the  Archiv  fur 
Naturgeschichte)  all  prepared  in  the  interest  of  medical  men, 
and  treat  their  various  subjects  mainly,  if  not  exclusively,  from 
the  medical  standpoint.  The  two  publications  now  to  be  men- 
tioned are,  on  the  contrary,  adapted  primarily  to  the  needs  of 
zoologists.  I  refer,  of  course,  to  the  Zoological  Record  and  to 
the  Zoologischer  Jahresbericht,  issued  by  the  Zoological  Station 
at  Naples. 

The  Zoological  Record  was  founded  by  Dr.  Albert  C.  L.  G. 
Giinther,  who  states  in  the  preface  to  the  first  volume,  covering 
the  literature  of  1864,  that  "the  object  of  the  Record  is  to 
give  in  an  annual  volume  reports  on,  abstracts  of,  and  an  index 
to  the  various  zoological  publications  which  have  appeared  in 
the  preceding  year  ;  to  acquaint  zoologists  with  the  progress  of 
every  branch  of  their  science  in  all  parts  of  the  globe ;  and  to 
form  a  repertory  which  will  retain  its  value  for  the  student  of 
future  years."  The  Zoological  Record  has  to  a  certain  extent 
attained  its  objects,  and  is,  indeed,  an  invaluable  aid  in  finding 


1 64        •  BIOLOGICAL   LECTURES. 

the  literature  of  any  subject.  It  has  suffered  in  reputation 
very  much,  owing  to  its  incompleteness,  its  omissions  being 
very  numerous,  and  too  often  both  surprising  and  inexcusable. 
You  have  only  to  compare  the  volumes  from  Naples  with  those 
of  the  Record  for  the  corresponding  years  to  satisfy  your- 
selves that  the  criticism  made  is  perfectly  just.  When,  there- 
fore, you  consult  the  Record,  you  will  usually  find  that  there 
are  other  perhaps  important  articles  on  your  subject  besides 
those  cited  in  the  Record.  The  English  standard  of  bibliog- 
raphy appears  to  me  not  to  be  very  high  either  in  regard  to 
practical  details  of  arrangement,  or  in  regard  to  thoroughness. 
I  remember  that  when  Mr.  Scudder  prepared  his  list  of  sci- 
entific serials  he  found  a  large  number  which  were  entirely 
overlooked  by  the  Royal  Society  in  their  great  catalogue.  In 
1870  a  special  association  was  formed,  which  many  naturalists 
joined,  for  the  object  of  continuing  the  Record.  In  1887  the 
publication  was  assumed  by  the  Zoological  Society.  The 
yearly  Record  is  sometimes  more  or  less  incomplete  ;  thus  in 
the  volume  for  1894  the  reports  on  Crustacea,  Arachnida, 
Myriapods,  and  Vermes  are  lacking.  Incredible  as  it  seems  in 
such  a  work,  there  is  no  index  of  authors,  but  only  an  index  of 
new  genera !  In  fact,  the  Record  has  its  chief  value  as  an 
assistance  to  the  systematic  zoologist. 

The  Zoologischer  Jahresbericht,  published  by  the  Zoological 
Station  at  Naples,  is  a  very  thorough  and  admirable  work.  Its 
first  seven  volumes  (i  879-1 885)  covered  the  whole  field  of 
zoology,  but  since  then  it  has  omitted  all  systematic  work, 
leaving  that  for  the  Record.  Its  matter  is  well  arranged, 
and  so  indexed  and  printed  that  it  is  easy  to  find  what 
one  seeks.  In  brief,  it  is  indispensable  for  every  zoological 
laboratory  in  which  anything  higher  than  elementary  work 
is  attempted. 

B.  Periodical  Bibliographies.  —  Under  this  head  we  have 
to  pass  in  review  a  series  of  journals  appearing  at  short  inter- 
vals. These  journals  form  two  natural  classes  :  first,  those 
specially  devoted  to  bibliography,  all  of  which  publish  short 
original  articles ;  second,  those  which  are  chiefly  devoted  to 
short  abstracts  of  articles  published  elsewhere. 


BIBLIOGRAPHY,  — A    STUDY  OF  RESOURCES.       165 

First  Class  (mainly  bibliographical).  —  i.  Zoologischer 
Anzeiger.  This  valuable  publication  is  probably  well  known 
to  you  all.  It  was  founded  in  1878  by  the  veteran  zoolo- 
gist, Victor  Carus,  and  publishes  at  frequent  intervals  lists 
of  articles  grouped  according  to  the  class  to  which  they 
refer.  This  plan  secures  relatively  prompt  publication  of 
the  titles,  but  has  the  disadvantage  that  consultation  of 
the  completed  volumes  is  exceedingly  laborious,  for  one  has 
to  look  through  lists  scattered  irregularly  through  the  pages. 
Owing  to  the  enormous  growth  of  zoological  literature  it  was 
found  necessary  to  divide  the  Anzeiger  into  a  volume  for 
original  articles  and  another  exclusively  for  bibliography. 

2.  Anatomise  her  Anzeiger.  This  journal  resembles  the 
Zoologischer  Anzeiger  very  closely  in  plan  and  appearance,  but 
differs  somewhat  in  its  scope,  for  it  confines  itself  to  the  litera- 
ture which  interests  the  student  of  vertebrate  morphology,  and 
classifies  the  titles  according  to  the  organs  to  which  the  papers 
refer.  This  magazine  was  founded  in  1886  by  Karl  Bardeleben, 
of  Jena,  and  is  now  the  ofificial  organ  of  the  German  Anatom- 
ical Society,  whose  proceedings  are  issued  as  an  Ergdnzungsheft 
of  the  Anzeiger. 

3.  Bibliographie  anatomiqiie.  A  journal  of  the  same  general 
character  as  the  last,  but  its  bibliographical  lists  are  confined 
exclusively  to  articles  published  not  in  France  but  in  French, 
—  a  restriction  which  necessarily  appears  somewhat  absurd 
as  well  as  characteristically  provincial  to  us.  The  journal, 
nevertheless,  is  an  excellent  one,  and  contains  valuable  original 
articles,  and  a  certain  number  of  abstracts,  which  are  usually 
good.  It  is  edited  by  Professor  Nicolas,  of  Nancy,  and  was 
started  in  1893. 

4.  Monitore  zoologico.  This  little  magazine  is  one  which 
ought  to  be  more  widely  known  in  America,  and  deserves 
general  support.  It  set  the  model  for  the  French  publication 
last  mentioned,  for  it  was  started  several  years  earlier,  having 
begun  in  1890.  It  gives  original  articles,  abstracts,  and  lists 
of  papers  on  zoological  and  morphological  subjects,  published 
by  Italians,  whether  in  the  Italian  language  or  not.  Now 
there  is  a  great  deal  of  important  investigation  accomplished 


1 66  BIOLOGICAL   LECTURES. 

in  Italy,  but  owing  to  entire  lack  of  first-class  scientific  jour- 
nals in  Italian,  the  results  of  these  investigations  are  issued  in 
all  sorts  of  ways,  —  oiten  in  little-known  medical  journals  or 
in  the  transactions  of  obscure  scientific  societies,  with  which 
Italy  swarms,  — and  they  would  remain  permanently  unknown 
were  it  not  for  the  painstaking  records  of  Professor  Chiarugi 
in  his  Monitore. 

The  four  serials  just  mentioned  ought  to  be  accessible  to 
every  student  and  to  form  part  of  the  library  of  every  zoolog- 
ical or  morphological  laboratory.  The  remaining  serials  to  be 
enumerated  are  certainly  less  essential,  but  for  certain  special 
purposes  are  almost  indispensably  consulted.     They  form  my 

Second  Class  (journals  primarily  devoted  to  publishing 
abstracts  of  papers).  —  I  have  noted  the  following  :  — 

1 .  Medizmisckes  Centralblatt,  founded  in  i863,by  L.  Hermann. 

2.  Biologisches  Centralblatt,  founded  in  1 88 1,  by  J.  Rosenthal. 

3.  Gynaekologisches  Centralblatt,  founded  in  1877,  by  Dr.  H. 
Fehling,  of  Stuttgart,  and  Dr.  H.  Fritsch,  of  Halle. 

4.  Neurologisches  Centralblatt,  founded  in  1 882,  by  E.  Mendell. 

5.  Physiologisches  Centralblatt^  founded  in  1887,  by  S.  Exner 
and  J.  Gad. 

6.  Zoologisches  Centralblatt,  founded  in  1 894,  by  A.  Schuberg. 

7.  Fortschritte  der  Medizin,  founded  in  1883,  by  C.  Fried- 
lander. 

8.  Journal  of  the  Royal  Microscopical  Society  of  London  gives 
numerous  good  abstracts  of  articles  interesting  to  microscopists, 
was  begun  in  1878,  is  now  issued  in  bi-monthly  parts,  forming 
a  bulky  annual  volume. 

9.  Virchow-Hirsch  Jahresberichte,  founded  in  1866  as  the 
continuation  of  an  earlier  medical  Jahresbericht  published  at 
Erlangen. 

10.  Schmidt's  JahrbUchery  which  was  founded  in  1834  and 
has  grown  into  a  series  of  nearly  two  hundred  and  fifty  vol- 
umes. These  Jahrbilcher  are  literally  indispensable  for  look- 
ing up  certain  lines  of  research  through  the  past,  as,  for 
example,  the  determination  of  sex,  the  phenomena  of  puberty, 
menstruation,  growth,  anatomy,  and  physiology  of  infancy, 
senile  metamorphoses,  heredity,  etc.     On   all  these    subjects 


BIBLIOGRAPHY,  — A    STUDY  OF  RESOURCES.       1 67 

Schmidt' s  Jahrbucher  will  guide  you  to  many  articles  of  bio- 
logical interest,  which  you  are  little  likely  to  discover  otherwise. 

It  often  happens  that  one  cannot  obtain  a  certain  original 
paper  when  needed,  and  in  such  cases  an  abstract  of  the  paper 
wanted  may  be  found  in  one  or  several  of  the  ten  serials  just 
enumerated.  You  will  notice  that  many  of  them  are  medical 
journals,  and  yet  they  are  sometimes  indispensable  to  the 
zoologists  and  morphologists.  For  example,  articles  on  the 
uterus  and  placenta,  on  growth,  heredity,  origin  of  sex,  and 
many  other  subjects  are  often  to  be  discovered  through  medi- 
cal publications,  and  through  medical  publications  only. 

You  have  doubtless  all  been  struck  with  the  fact  that  nearly 
all  the  titles  I  have  quoted  are  in  German  or  in  Latin  by  Ger- 
man authors,  and  have  already  reached  the  conclusion  that  the 
work  of  the  world  in  recording  biological  literature  is  mainly 
the  work  of  Germans.  This  conclusion  is  correct,  and  it  is  a 
pleasure  to  make  a  public  acknowledgement  of  our  indebted- 
ness. Hereafter,  we  hope  that  a  systematic  and  thorough 
record  of  zoological  and  anatomical  literature  will  be  kept  by 
the  International  Bureau  organized  at  Zurich  through  the 
efficient  energy  of  our  countryman  Mr.  H.  H.  Field.  We 
should  each  look  upon  it  as  a  personal  obligation  to  support 
the  work  of  this  Bureau,  both  by  cooperating  with  it  and  by 
subscribing  to  its  publications. 

To  conclude  :  how  is  one  to  proceed  if  one  wishes  to  find 
the  literature  of  a  given  zoological  or  morphological  subject.'' 
I  should  answer :  consult  first  the  principal  text-books  at  your 
command,  which  will  give  you  probably  some  of  the  chief 
authorities,  by  turning  to  which  you  will  obtain  other  refer- 
ences; and  from  the  papers  thus  traced  yet  other  references 
will  be  secured.  Unless  one  is  dealing  with  some  minor  or 
detailed  question,  or  some  novel  or  unusual  topic,  one  can 
usually  obtain  acquaintance  with  a  considerable  body  of  inves- 
tigations with  comparative  rapidity.  Next,  one  must  consult 
the  standard  bibliographies  (p.  1 56),  and  also  both  the  various 
Jahi'esberichte  and  the  current  bibliographies  (especially  of  the 
Zoologischer  and  of  the  Anatomischer  Anzeiger).  Third,  con- 
sult Milne-Edwards'  Physiologie  and  Bronn's  Thierreich  ;  or,  if 


1 68  BIOLOGICAL  LECTURES. 

you  can  find  any  important  monograph  which  certainly  or 
probably  deals  with  your  subject,  consult  that,  of  course. 
Finally,  if  your  question  is  one  medical  men  are  likely  to  have 
discussed,  look  through  the  Reports  of  Virchow-Hirsch  and 
Schmidt's  Jahrbilchery  and  also  through  the  various  medical 
journals  of  the  Centralblatt  type  (see  p.  i66,  above). 

I  have  dealt  with  a  difficult  and,  I  fear,  very  dry  subject, 
and  can  only  hope  that  some  of  my  suggestions  will  prove 
helpful.  It  is  profitable  to  consider  sometimes  the  ways  and 
means  of  science  as  well  as  her  results,  for  the  investigator's 
success  depends  upon  his  mastery  over  both  means  and  results, 
and  this  double  mastery  can  be  had  only  by  those  who  also 
command  the  complex  bibliographical  resources  of  biology.  I 
hope  that  our  review  of  these  resources  will  encourage  some  of 
you  to  enter,  others  to  advance  along  the  paths  of  research  ; 
and  I  trust  that  you  all,  when  you  leave  the  laboratory,  will 
carry  with  you  a  deeper  and  loftier  enthusiasm  for  original 
research,  which  is  at  once  the  chief  duty  and  the  chief  privi- 
lege of  the  biologist. 

Revised  at  Boston,  Dece?nber,  1895. 


ELEVENTH    LECTURE. 


THE    TRANSFORMATION    OF    SPOROPHYLLARY 
TO    VEGETATIVE    ORGANS.^ 

PROF.  GEORGE  F.  ATKINSON. 

(Cornell  University,  Ithaca,  N.Y.) 

The  general  effect  of  nutrition  in  plants  is  evident  in  their 
growth  and  fruiting  ;  but  the  more  subtle  influences,  under  a 
great  variety  of  changing  or  special  conditions,  are  but  imper- 
fectly understood.  In  general,  an  increase  in  food  supply 
within  the  plant,  external  conditions  being  favorable,  increases 
the  entire  plant  product.  In  poor  soil  plants  may  be  fed  with 
profit,  the  product  increasing,  though  not  in  the  same  ratio, 
with  the  increased  supply  of  food.  Not  only  is  the  vegetative 
part  of  the  plant  increased,  but  the  fruit  also,  within  certain 
limits.  The  ratio  of  increase,  however,  between  the  vegetative 
portion  of  the  plant  and  its  fruit  is  not  constant,  but  changes 
with  the  varying  food  supply.  After  a  given  point  the  vegeta- 
tive portion  increases  more  rapidly  than  the  fruit.  Another 
striking  influence  of  increased  food  supply  is  that  a  point  is 
reached  soon  where  the  fruit  portion  decreases,  or  is  even  com- 
pletely suppressed,  while  the  vegetative  portion  still  increases. 
Our  knowledge  of  these  disproportionate  and  antagonistic 
relationships  between  the  vegetative  and  reproductive  portions 
of  the  plant  is  largely  empirical,  though  some  of  it  is  based  on 
direct  experimentation.  It  is  not  surprising,  therefore,  that 
even  among  botanists  there  should  be  differences  of  opinion 
concerning  the  fundamental  laws  governing  these  relationships. 

The  genus  Onoclea,  as  well  as  some  others,  presents  an 
interesting  dimorphism  of  the  leaves,  some  of  the  leaves  being 

1  See  Plates  I-VIII  at  close  of  volume. 


lyo  BIOLOGICAL   LECTURES. 

devoted  exclusively  to  the  vegetative  function,  while  others  are 
devoted  exclusively  to  the  reproductive  function.  In  Onoclea 
the  vegetative  leaf  forms  a  large  expanded  triangular  lamina, 
which  is  divided  into  several  large  pinnae  with  rudimentary 
lobes  or  pinnules.  The  reproductive  leaves,  or  sporophylls, 
are  built  on  much  the  same  general  plan,  but  are  much  shorter, 
with  the  pinnae  and  pinnules  also  much  shorter  and  narrower, 
and  the  edges  inrolled,  entirely  concealing  the  sporangia,  as  if 
they  were  enclosed  in  carpellary  structures,  though  the  sporo- 
phyll  has  not  become  a  closed  structure,  such  as  is  found  in 
the  ovary  of  higher  plants.  The  inrolled  pinnae  are  closely 
appressed  against  the  rachis  of  the  sporophyll. 

Besides  this  structural  dimorphism  of  the  leaves  they  present 
what  is  sometimes  termed  a  seasonal  dimorphism,  —  i.e.  the 
vegetative  leaves  are  the  first  to  appear  in  the  season,  from 
April  and  May  until  July,  while  the  sporophylls  appear  in  July, 
or  the  latter  part  of  June.  During  the  first  part  of  the  season 
the  vegetative  or  nutritive  system  of  the  plant  is  built  up, 
while  during  the  latter  part  of  the  season  the  reproductive 
function  is  in  the  ascendant.  Occasionally  an  abnormal  state 
of  the  leaf  in  Onoclea  sensibilis  is  found,  in  which  both  func- 
tions are  united  in  a  single  leaf,  a  portion  of  the  leaf  being 
expanded  and  resembling  the  vegetative  leaf,  while  some  of 
the  pinnae  are*  more  or  less  rudimentary,  revolute,  and  sporif- 
erous,  representing  an  intermediate  stage  between  the  truly 
vegetative  leaf  and  the  typical  sporophyll.  This  form  of  the 
leaf  was  once  described  as  a  variety  —  obttisilobata  Torrey  — 
of  this  species  of  Onoclea,  though  later  it  was  regarded  as  "■  a 
rare  abnormal  state  in  which  the  pinnae  of  some  of  the  sterile 
fronds,  becoming  again  pinnatifid,  and  more  or  less  contracted, 
bear  some  fruit  dots  without  being  much  revolute  or  losing 
their  foliaceous  character."  ^  The  language  here  suggests  that 
the  sterile  leaf  becomes  partly  transformed  into  a  fertile  leaf, 
in  accordance  with  the  old  ideas  of  metamorphosis.  More 
recently,^  from  the  discovery  of  a  number  of  the  forms  of  this 

1  Gray's  Manual,  5th  ed.,  p.  668.  The  same  form  of  the  plant  was  known  as 
the  species  O.  obtusilobata  Schkuhr,  idem. 

^  Underwood  :  Bull.  Torr.  Bot.  Club,  Vol.  VIII  ;  Bot.  Gaz.,  1881,  p.  loi. 


TRANSFORMATION  OF  SPOROFHVLLARV.  171 

species  in  a  meadow,  it  was  suggested  that  this  state  resulted 
from  some  injury  to  the  sterile  leaf,  so  that  the  vegetative 
function  was  forced  upon  the  very  young  sporophylls,  causing 
them  to  expand  more  or  less,  while  the  sporangia  and  sori  were 
correspondingly  decreased.  This  suggestion  met  with  consid- 
erable opposition.  Later  the  suggestion  was  adopted  and  pub- 
lished by  another,  and  upon  this  the  following  criticism  appeared 
in  Nature,  April  15,  1894  :  **The  remark  quoted  .  .  .  about  the 
probable  cause  of  the  cases  where  the  fronds  of  Onoclea  have 
an  intermediate  character  between  the  usual  sterile  and  fertile 
conditions,  is  one  of  those  sage  observations  which  it  is  easy  to 
make,  but  which  observed  facts  hardly  or  not  at  all  sustain." 

Although  an  experiment  had  been  planned  for  the  purpose 
of  attempting  to  induce  this  form  artificially  by  cutting  off  the 
early  vegetative  leaves,  this  criticism  really  *'  set  the  machinery 
in  motion,"  for  without  experimental  proof  such  an  empirical 
proposition  lacked  an  essential  foundation  for  argument.  The 
locality  selected  for  carrying  on  the  experiment  was  in  the 
vicinity  of  Ithaca,  N.Y.,  on  the  flats  not  far  from  the  head  of 
Cayuga  Lake.  The  first  cutting  of  the  leaves  was  made  May  1 1, 
when  they  were  twelve  to  eighteen  inches  high.  It  was  feared 
at  the  time  that  the  experiment  had  been  postponed  too  long 
to  obtain  the  desired  results,  as  it  seemed  within  the  bounds 
of  possibility  that  already  the  vegetative  function  might  have 
been  carried  on  for  a  sufficient  time  for  the  manufacture  of 
what  carbohydrates  the  plant  would  need  for  the  perfect 
development  of  the  reproductive  portion.  The  intention  was 
then  to  cut  the  leaves  about  once  each  week,  in  order  that  the 
plants  could  derive  very  little  benefit  from  the  later  developed 
sterile  leaves.  Heavy  rains,  however,  prevented  access  to  the 
localities  until  June  9,  when  the  leaves  were  cut  a  second  time. 
The  second  leaves  had  reached  approximately  the  same  size  as 
the  first  crop,  and  still  by  this  time  there  was  no  sign  of  the 
development  of  the  fertile  leaves,  either  in  the  experiment  plat 
or  in  adjacent  plants  which  had  been  left  as  checks. 

July  12  a  third  visit  was  made  to  the  locality  on  the  Ithaca 
flats,  where  the  larger  number  of  ferns  were.  Diligent  search 
at  this  time  revealed  nothing  which  at  first  could  be  under- 


172 


BIOLOGICAL   LECTURES. 


stood  to  be  the  fertile  leaf  in  the  experiment  plat,  and  the 
knife  was  used  for  the  third  time.  While  cutting  the  third 
crop  of  leaves  occasionally  one  was  seen  which  appeared  quite 
different  from  the  ordinary  sterile  leaves.  The  pinnules  were 
fully  expanded,  and  the  lobes  appeared  nearly  normal  in  form, 
but  the  venation  was  somewhat  more  prominent,  and  this  gave 
the  appearance  which  first  attracted  attention.  After  critical 
examination  there  were  seen  peculiar  and  very  small  whitish 
flakes  or  scales  on  the  under  surface  of  the  pinnules.  These, 
with  the  aid  of  a  pocket  lens,  were  readily  seen  to  be  partially 
aborted  indusia,  located  either  directly  across  or  at  the  side  of 
the  veinlets.  The  pleasure  at  the  discovery  of  this  result  was 
considerably  dampened  by  the  thought  that  the  experiment 
might  prove  to  have  been  too  radical  by  cutting  the  leaves 
more  than  once.  Further  examination  revealed  what  appeared 
to  be  still  younger  fertile  leaves  which  would  not  be  so  fully 
expanded  when  grown.  At  this  date  there  were  observed  in 
the  adjacent  undisturbed  plants  several  normal  sporophylls 
partially  developed.  July  29  another  examination  was  made, 
and  quite  a  number  of  leaves  were  found  which  would  be  taken 
for  quite  typical  cases  of  the  form  of  the  species. 

August  8  and  9,  all  the  plants  showing  these  results  were 
gathered  and  photographed,  a  portion  of  the  stem,  or  rhizome, 
was  taken  with  each  plant  in  order  to  show  some,  at  least,  of 
the  bases  of  the  leaves  which  had  been  amputated,  as  well  as 
the  recently  developed  sterile  leaves  for  comparison.  Nearly 
thirty  such  plants  were  gathered,  and  more  than  twenty  of  these 
were  photographed,  in  order  to  preserve  an  accurate  record  of 
the  many  variations  which  presented  themselves. 

In  the  normal  sporophyll,  the  pinnae  are  quite  closely 
approximated  on  one  side  of  the  rachis.  The  fertile  pinnules 
are  closely  revolute,  and  the  margins  very  much  shortened,  so 
that  each  pinnule  forms  a  small,  oval,  pocket-shaped  or  slipper- 
shaped  sack,  open  only  at  a  point  near  the  attachment  with 
the  mid-vein  of  the  pinna.  These  pinnules  possess  two  to  four 
pairs  of  lateral  veinlets.  Upon  these  lateral  veinlets  are  the 
placentae,  seated  rather  near  the  base,  and  the  true  indusium 
is  situated  across  the  base  of  the  veinlet,  near,  or  a  little  dis- 


TRANSFORMATION  OF  SPOROPHYLLARY.  173 

tant  from,  the  mid-vein,  and  arches  slightly  outward,  or  away 
from  the  mid-vein,  partially  covering  the  group  of  sporangia. 

The  first  step  in  the  transformation  of  the  sporophyll  is  the 
lateral  spreading  of  the  pinnae,  so  that  they  stand  out  more  or 
less  strongly  in  a  plane  corresponding  to  that  of  the  vegetative 
leaf.  At  the  same  time  there  occurs  a  partial  unfolding  of  the 
revolute  pinnule.  This  occurs  by  an  increase  in  the  number 
of  cells  of  the  lamina,  and  a  corresponding  decrease  in  the 
growth  of  the  cells  which  go  to  form  the  sori.  The  marginal 
cells  of  the  lamina  increase  more  rapidly  than  those  toward 
the  mid-vein  and  the  base.  A  few  of  the  terminal  pinnae  in  the 
normal  sporophyll  bear  no  pinnules,  but  are  very  much  like 
the  pinnules  of  the  lower  pinnae.  The  simplest  condition  of  the 
unfolding  of  the  revolute  pinnae  or  pinnules  is  the  partial 
expansion  of  these  terminal  ones,  more  advanced  stages  pro- 
ceeding along  down  from  the  terminal  portions  of  the  pinnules. 

The  grades  of  transition  are  correlated  with  the  circinate 
development  of  the  leaf,  the  later  developed  portions  showing 
a  more  highly  developed  vegetative  expansion  and  function 
than  the  early  developed  portions  of  the  same  leaf.  The  pinnae 
then,  in  the  simplest  and  intermediate  stages,  have  a  more 
or  less  clavate  or  spathulate  outline.  The  pinnules  in  an  indi- 
vidual pinna  may  vary  from  quite  strongly  revolute  ones  to 
those  which  are  fully  expanded  and  nearly  plane. 

Occasionally  transformed  fertile  leaves  are  found  which  show 
a  tendency  to  an  abortive  development,  i.e.  they  remain  quite 
small,  the  stipe  rather  short,  the  pinnae  and  pinnules  very 
short,  though  they  may  be  quite  fully  expanded. 

Comparing  individual  sporophylls,  all  grades  of  transition  are 
present  from  the  completely  differentiated  fertile  leaf  to  the 
sterile  one.  In  several  cases  it  was  impossible  to  determine 
with  certainty  to  which  phase  of  the  dimorphism  the  leaf  pri- 
marily belonged,  or  for  which  it  was  originally  intended.  Some 
of  these  leaves  which  were  at  first  doubtful  were  finally  found 
to  possess  rudimentary  indusia  on  a  few  of  the  lower  pinnae, 
these  occurring  on  the  basal  pinnules. 

The  fully  or  partially  expanded  pinnules,  when  the  transfor- 
mation has  not  been  carried  too  far,  are  more  or  less  obtuse. 


174  BIOLOGICAL   LECTURES. 

The  venation  also  is  very  prominent,  and  strong  in  contrast 
with  that  of  the  sterile  leaf,  especially  the  lateral  veinlets  of 
the  pinnules.  This  character  is  quite  persistent,  and  enables 
one  to  differentiate  the  leaves  frequently  when  no  indusia  are 
present,  and  the  pinnules  are  not  obtuse,  or  no  more  so  than 
those  of  the  normal  sterile  leaves. 

One  transformed  sporophyll  had  a  length  of  twenty-five  cm., 
and  a  spread  of  pinnae  twenty-two  cm.  in  extent.  A  very  few 
of  the  basal  pinnules  had  their  margins  slightly  revolute,  and 
quite  a  number  of  indusia  were  present,  while  very  few  of  the 
pinnules  were  obtuse.  The  venation  of  the  entire  leaf  was 
quite  coarse  and  very  prominent. 

During  the  expansion  of  the  pinnules,  the  position  of  the 
indusia  changes  somewhat,  and  its  form,  to  a  very  great  extent. 
It  becomes  located  at  a  greater  distance  from  the  base  of  the 
lateral  veinlets,  the  distance  depending  to  some  extent  upon 
the  extent  of  the  transformation  of  the  pinnule.  In  broadly 
expanded  pinnules  at  the  termination  of  the  pinnae,  the  indusia 
are  frequently  moved  on  to  veinlets  of  the  second  and  third 
order,  instead  of  those  of  the  first  order. 

While  indusia  are  present  on  partially  or  nearly  expanded 
pinnules,  or  frequently  on  fully  expanded  ones,  sporangia 
appear  to  occur  only  on  those  which  are  entirely  normal,  or 
only  partially  expanded.  Passing  through  the  various  transi- 
tions of  the  pinnules,  from  the  normal  fertile  ones  to  those 
which  are  little  more  than  half  expanded,  the  sporangia  vary, 
gradually  decreasing  in  number  and  perfection  of  development, 
as  the  pinnules  partake  more  and  more  of  the  vegetative  char- 
acter. In  the  partially  expanded  pinnules,  the  indusium  is  fre- 
quently so  small  that  it  affords  very  little  protection  to  the 
sporangia,  and  the  location  of  rudimentary  sporangia  is  often 
at  a  considerable  distance  from  the  indusium. 

When  the  leaf  has  lost  so  much  of  its  reproductive  function 
that  the  sporangia  are  becoming  rare  or  rudimentary  in  the 
sorus,  apospory  frequently  occurs,  and  the  placenta  develops 
among  the  rudimentary  sporangia  prothalloid  growths.  These 
are  filamentous,  lanceolate,  or  spathulate  in  form,  the  two  latter 
forms  being  two  or  more  cells  wide.     The  cells  are  richly  pro- 


TRANSFORMATION   OF  SPOROPHYLLARY.  175 

vided  with  chlorophyll,  but  thus  far  no  antheridia  or  arche- 
gonia  have  been  found.  These  prothalloid  growths  resemble 
very  much  some  of  those  which  are  developed  from  the  placen- 
tal region  of  Pteris  aqiiilina  L.,  and  first  described  by  Doctor 
Farlow  in  the  Annals  of  Botany,  II,  1888,  p.  383.  The  same 
condition  of  Pteris  aquilina  was  noted  by  myself  in  the  autumn 
of  1893,  at  Ithaca,  N.  Y. 

When  the  experiment  with  Onoclea  sensibilis  was  undertaken, 
no  serious  thought  was  given  to  an  attempt  to  produce  like 
conditions  by  artificial  treatment  with  the  other  species  of  this 
genus,  namely,  Onoclea  struthiopteris.  However,  on  July  14, 
after  observing  the  result  which  was  attending  the  experiment 
with  Onoclea  sensibilis,  I  determined  to  try  the  Onoclea  struthi- 
opteris even  at  this  late  date.  The  fern  is  very  abundant  on 
an  island  in  Fall  Creek,  where  vegetation  is  very  rank  and  the 
leaves  of  the  ostrich  fern  attain  a  height  of  150  cm.  or  more. 
The  leaves  from  fifty  or  sixty  stools  of  this  fern  were  cut 
away,  the  leaves  then  having  attained  their  maximum  height 
for  this  locality.  In  this  number  of  stools  there  were  half  a 
dozen  in  which  there  were  fertile  leaves  already  15-25  cm.  in 
height. 

The  experiment  was  inspected  on  August  10.  The  fertile 
leaves  which  were  up  on  the  14th  of  July  had  matured  their 
sporangia  and  were,  to  all  appearance,  normal.  There  were 
many  rudimentary  fertile  leaves  only  partly  unrolled,  three  to 
six  inches  in  height.  These  were  also  found  among  the  stools 
of  the  fern  which  had  not  been  disturbed.  For  a  long  time 
during  the  spring,  the  ground  here  was  under  water,  and  this 
may  have  had  some  influence  in  aborting  many  of  these  leaves. 
That  many  of  them  were  of  the  fertile  kind  was  manifest  by  the 
peculiar  revolute  character  of  the  rudimentary  pinnules. 

Very  few  of  the  stools  from  which  the  leaves  had  been  cut 
on  the  14th  of  July  had  put  forth  new  leaves.  Ten  or  twelve 
had  produced  one  to  four  leaves,  ranging  from  one  to  two  feet 
high.  Very  careful  search  was  made  to  discover  some  sign  of 
a  sporophyll  partially  transformed,  and  I  was  about  to  conclude 
that  the  experiment  was  a  failure  for  that  year  because  entered 
upon  at  so  late  a  date.     At  last  a  single  leaf  was  found  in  a 


176  BIOLOGICAL  LECTURES. 

stool  where  were  three  freshly  developed  sterile  leaves.  The 
sterile  leaves  were  60-75  cm.  in  height,  and  the  transformed 
sporophyll  about  30  cm.  The  leaf  was  somewhat  injured  by 
accident,  perhaps  by  the  knife  when  cutting  the  sterile  leaves 
on  the  14th.  The  pinnae  were  fully  expanded,  yet  markedly 
different  from  those  of  the  sterile  leaves,  being  only  toothed, 
while  the  pinnae  of  the  sterile  leaves  are  deeply  cut  and  possess 
quite  acute  pinnules.  The  teeth,  or  pinnules,  of  the  trans- 
formed fertile  leaf  were  obtuse  or  rounded.  This  was  the  only 
marked  difference  at  first  observed,  and  I  did  not  feel  warranted 
in  concluding  that  it  was  a  fertile  leaf  until  examination  with  a 
pocket  lens  revealed  plainly  a  number  of  rudimentary  indusia. 
There  were  no  sporangia,  however,  not  even  rudimentary  ones, 
and  none  of  the  pinnules  were  at  all  revolute. 

The  experiment  with  Onoclea  striithiopte}is  being  somewhat 
unsatisfactory,  because  undertaken  so  late  in  the  season,  was 
renewed  this  year  (1895).  The  first  vegetative  leaves  were  cut 
early  in  May,  when  they  were  about  40  or  50  cm.  long.  This 
species  differs  markedly  from  Onoclea  sensibilis  in  the  vernation 
of  the  leaves.  Those  of  Onoclea  sensibilis  are  developed  suc- 
cessively one  by  one  on  a  prostrate  rhizome,  or  stem,  which 
advances  so  rapidly  that  the  leaves  of  one  season  stand  in  a 
row.  In  Onoclea  struthiopteris  the  stem  is  perpendicular  and 
increases  in  length  very  slowly,  the  leaves  being  developed  in 
rosettes,  a  half  dozen,  more  or  less,  at  one  time. 

The  experiment  plat  was  visited  a  second  time  early  in  June, 
and  a  second  rosette  of  leaves  had  developed  from  the  stools 
which  had  been  cut  in  May.  This  time  the  leaves  were  about 
30  cm.  high.  None  of  the  sporophylls  had  appeared,  and  the 
leaves  were  cut  again.  Leaves  from  undisturbed  plants  were 
also  cut  at  this  date.  Late  in  June  a  few  of  the  sporophylls 
were  appearing  from  a  very  few  of  the  untreated  plants,  but 
none  as  yet  showed  from  the  amputated  plants,  though  another 
large  rosette  of  vegetative  leaves  had  developed.  The  season 
was  a  very  dry  one,  and  very  few  sporophylls  had  developed, 
and  for  this  reason  the  experiment  was  considered  a  failure. 
However,  July  29th  a  sudden  impulse  seized  me  to  visit  the  ex- 
periment plat  again,  and  this  time  not  in  vain,  for  eight  to  ten 


TRANSFORMATION  OF  SPOROPHYLLARY.  I  77 

plants  had  each  from  one  to  four  partially  transformed  sporo- 
phylls.  These  presented  a  great  variety  of  stages  in  the  transi- 
tion, though  in  no  case  had  the  transformed  sporophylls  reached 
the  size  and  expansion  of  the  vegetative  leaves  as  in  the  case 
of  Oiioclea  scnsibilis.  They  were  quite  young,  however,  and 
probably  later  in  the  season  would  have  been  larger  and  more 
expanded. 

These  plants  were  nearly  all  removed  to  the  laboratory  at 
the  time  in  order  to  photograph  and  study  them.  In  general 
the  transformation  of  the  sporophylls  of  Onoclea  striithiop- 
teris  agrees  with  that  of  Onoclea  sensibilis  in  that  the  distal 
portion  of  the  leaf  and  of  the  pinnae  expand  more  than  the 
proximal  portion,  these  latter  parts  bearing  either  normal  sporan- 
gia and  sori,  or  showing  them  in  various  stages  of  degradation 
and  suppression.  At  that  time  no  prothalloid  growths  could  be 
discerned  with  the  eye,  or  with  the  aid  of  a  pocket  lens.  Per- 
haps they  might  appear  later  in  the  season,  since  the  sporophylls 
were  much  younger  than  those  on  Onoclea  sensibilis  on  which 
they  occurred. 

The  results  of  these  experiments  are  entirely  in  harmony 
with  a  law  which  many  recognize  to  exist  between  the  vegetative 
and  reproductive  functions  of  plants,  and  indeed  animals  as 
well.  They  serve,  however,  to  demonstrate  clearly  this  relation 
which  in  many  cases  has  been  observed  empirically  rather  than 
demonstrated  by  definite  tests.  In  these  ferns,  the  fact  that 
there  is  a  complete  differentiation  between  the  sterile  and  fertile 
leaves,  and  that  the  sterile  leaves  develop  quite  far  in  advance 
of  the  fertile  ones,  makes  the  case  peculiarly  adapted  to  present 
a  beautiful  demonstration  of  the  law.  A  certain  development 
of  the  vegetative  phase  is  necessary  in  order  to  provide  for  the 
necessary  nutriment  which  the  reproductive  phase  requires.  If 
the  vegetative  leaves  are  destroyed  or  removed  before  this  func- 
tion is  so  far  completed  as  to  enable  the  complete  development 
of  the  reproductive  phase,  the  latter  will  necessarily  decrease, 
and  there  will  be  an  effort  on  the  part  of  the  plant  to  provide 
as  quickly  as  possible  for  the  furtherance  of  the  vegetative 
functions.  This  can  most  quickly  be  attained  by  the  partial  or 
complete  expansion  of  leaves  which  had  begun  to  be  differen- 


IjS  BIOLOGICAL   LECTURES. 

tiated  as  fertile  ones,  for  the  general  plan  of  structure  of  the 
sterile  and  fertile  leaves  is  very  much  the  same,  especially  in  a 
very  early  stage  of  their  development.  The  different  degrees 
of  fixation  of  the  reproductive  characters  on  these  very  young 
fertile  leaves,  at  the  time  when  the  plant  is  suddenly  deprived 
of  the  fully  developed  vegetative  leaves,  determines  to  a  great 
extent  the  individual  character  of  the  transformed  structure 
which  assumes  the  responsibility  for  the  entire  labor  of  the  leaf 
system  heretofore  definitely  divided  between  different  individual 
leaves  or  structures.  This  individual  character  is  also  influ- 
enced to  a  certain  extent  by  the  readiness  with  which  the  indi- 
vidual plant  puts  forth  new  vegetative  leaves.  So  with  the 
various  combinations  of  these  two  conditions  there  results  the 
very  wide  variation  which  is  here  presented  in  the  forms  of 
the  transformed  fertile  leaves,  showing  almost  every  conceivable 
gradation  which  we  could  naturally  expect  when  we  take  into 
consideration  the  course  of  development  of  the  ordinary  leaves. 
The  extremes  of  these  variations  present  very  doubtful  cases. 
On  the  one  hand,  there  are  fertile  leaves  which  have  felt  the 
slightest  touch  of  this  influence  controlling  the  transformation, 
and  it  is  extremely  difficult  to  say  whether  it  is  entirely  normal 
or  not.  On  the  other  hand,  there  are  cases  where  the  greatest 
demand  has  been  made  upon  a  leaf  of  the  fertile  kind  at  so 
early  a  period  in  its  development  that  it  becomes  to  all  intents 
and  purposes  a  vegetative  leaf,  and  possesses  so  little  of  the 
individuality  of  the  fertile  leaf  that  we  cannot,  in  our  ignorance, 
discriminate  it  from  a  leaf  of  the  vegetative  kind. 

The  plan  this  season,  though  not  carefully  originated,  was  to 
extend  the  experiments  to  phanerogamous  plants  in  order  to  see, 
especially,  if  the  pistils,  which  are  supposed  to  be  homologous 
sporophyllary  organs,  could  be  forced  to  take  on  the  form  and 
function  of  the  vegetative  leaves  by  cutting  off  the  latter.  This 
part  of  the  experiment,  I  say,  was  not  well  originated,  since, 
on  account  of  numerous  other  duties,  no  selection  of  plants 
was  made  until  operations  were  begun  in  the  spring.  For  this 
reason  some  of  the  plants  operated  on  were  too  far  advanced, 
while  others  were  ill  chosen,  because  the  sporophylls  appeared 
at  the  same  time  as  the  vegetative  leaves.     This  latter  difficulty 


TRANSFORMATION  OF  SPOROPHYLLARY.  179 

presented  itself  especially  in  the  case  of  Podophyllum  peltatum, 
Ariscema  tripJiylltirn,  and  Aralia  midicaulis.  In  Geranium 
macuiatumy  Smilacina  racetnosa^  Angelica  atropiirpiirea^  and 
Veratrum  viride  the  sporophyllary  organs  were  too  far  advanced. 

While  direct  experimental  evidence  seems  to  be  lacking, 
there  is  enough  of  empirical  evidence  to  show  that  the  trans- 
formation of  the  sporophyllary  organs  to  vegetative  ones  takes 
place  quite  frequently  in  certain  species  of  the  phanerogams. 

Transformations  of  the  andraecium,  or  stamens  (microsporo- 
phylls),  is  not  a  very  common  occurrence,  though  it  is  recorded 
in  the  case  of  several  species.  Petunia^  Jatropha  pohliana  Miill. 
(Muller,  Mem.  Soc.  Phys.  et  Hist.  Nat.,  Geneva,  Tome  XVII), 
Trifolium  repens,  cultivated  species  of  Rosa,  etc.  Transforma- 
tions of  the  pistils,  or  gynaecium  (macrosporophylls),  are  much 
more  common  and  remarkable.  In  the  double-flowering  cherry 
the  ovary  is  changed  often  to  a  small  foliar  organ,  frequently 
the  margins  separated  thus  exposing  the  ovules,  while  the  tip 
has  a  slender  style  and  imperfect  stigma.  Moquin  relates  a 
case  in  a  tulip  where  the  ovary  was  represented  by  true  leaves 
with  ovules  on  their  margins.  This  frequently  happens  in  the 
columbine  and  in  members  of  the  Cruciferae  and  Umbelliferse. 
In  Vitis  sometimes  the  pistil  is  foliaceous,  with  the  ovules  on 
their  inner  surface  (Planchon  et  Mares,  An7t.  Sci.  Nat,,  Ser.  5, 
Tome  VI,  p.  228,  1866).  If  the  ovary  is  the  homologue  of  the 
macrosporophyll  in  the  strobilus  of  the  Archegoniatae,  as  Bower 
suggests,  then  the  opening  of  the  ovary  and  the  exposure  of 
the  ovules,  or  macrosporangia,  under  the  influence  of  changed 
or  disturbed  conditions  of  nutrition,  must  be  looked  upon  as  a 
partial  reversion  inform  only,  not  a  reversion  in  function.  This 
is  accompanied  by  a  more  or  less  complete  sterilization  of  the 
sporogenous  tissue,  the  expansion  of  the  blade  into  a  well- 
developed  foliar  organ,  and  the  assumption  of  the  vegetative 
function  in  place  of  the  reproductive  one. 

The  philosophy  of  these  changes,  viewed  not  only  in  the  light 
of  immediate  causes,  but  also  from  the  standpoint  of  phylogeny 
of  the  foliar  organs  of  the  sporophyte,  teaches  that  they  proceed 
from  the  sporophyllary  to  the  vegetative  organs.  This  study 
has  led  rather  unexpectedly  to  questions  of  deeper  import  than 


l8o  BIOLOGICAL   LECTURES. 

were  in  mind  at  the  start.  It  suggests  more  than  the  mere 
adaptation  of  the  sporophyll  to  the  form  and  function  of  the 
vegetative  leaf,  directed  by  some  influence  which  tends  at  the 
time  to  force  that  function  on  it.  It  suggests  that  in  general 
vegetative  leaves  may  have  been  derived  from  sporophylls. 

In  other  words,  these  results  lend  force  to  the  proposition 
offered  by  Bower  {Ann.  Bot.y  VIII,  pp.  343-365,  1894)  that  the 
sporophylls  are  primary  organs,  the  vegetative  leaves  secondary 
ones,  and  that  sporophylls  never  have  been  derived  from  foliage 
shoots,  but  that  the  converse  is  true. 

Aside  from  the  questions  of  homology  and  phylogeny  of  foli- 
age shoots  and  sporophylls,  another  one  presents  itself,  which 
suggests  that  one  of  the  potent  influences  in  the  evolution  of 
vegetative  organs  on  the  sporophyte  was  a  disturbance  of  the 
carbon  assimilatory  function  of  the  gametophyte  in  the  gradual 
passage  of  plants  from  an  aquatic  to  a  terrestrial  life.  This  is 
a  purely  theoretical  consideration,  and  probably  must  always 
reniain  so,  though  it  is  quite  probable  that  artificial  injury  to  the 
gametophyte  could  be  made  to  result  in  the  sterilization  of 
sporogenous  tissue,  which  was  the  first  step  toward  the  evolu- 
tion of  sporophytic  vegetative  organs.  However,  considering 
the  sporophyte  alone,  we  have  seen  how  artificial  injury  can  be 
made  to  influence  the  advance  of  a  sporophyll  to  a  foliage  shoot 
within  a  single  life  cycle,  —  a  demonstration  of  phylogeny  in 
ontogeny. 


rRANSFORXfATlOX   OF  UPOROI'H VIJ.AKY.  iSl 


Y 


Pi.ATK  T.  —  Onoclea  Sensibilis,  normal  form. 


l82 


BIOLOGICAL   LECTURES. 


Plate  II.  —  Oiioclea  Sensibilis,  with  partially  transformed  sporophylls 


TRANSFORMATION   OF  SPOROPH YLLA RY.  183 


Plate  III.  —  Onoclea  Sensibilis,  with  partially  transformed  sporophyll. 


1 84 


BIOL  OGICA  L    A  EC  TURKS. 


PLATii  IV.  —  Onoclea  Sensibilis,  with  two  completely  transformed  sporophylls. 


TRANSFORMATION   OF  STOROTH  VLI.ARV.  I  85 


Plate  V.  —  Onoclea  Sensibilis.     a  normal  form  of  sporophyll.     b  partially  transformed 
sporophyll,  showing  "  fruit  dots." 


1 86 


BrOT. OGICA L    LECTURES. 


Plate  VI.  —  Ouoclea  Sensibilis,  lower  portion  of  partially  transformed  sporophyll  magnified. 


TRANSFORMATION  OF  SPOROPHVLLA RV.  187 


Plate  VII.  —  Onoclea  Struthiopteris.     The  four  small  leaves  are  sporophylls :  one  is  normal, 
the  others  partially  transformed. 


BIOLOGICAL   LECTURES. 


Plate  VIII.  —  Onoclea  Struthiopteris.     a  normal  sporophyll.     b  partially  transformed  sporo- 
phyll.     c  completely  transformed  sporophyll. 


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